diff --git a/administrator/components/com_joomlaupdate/config.xml b/administrator/components/com_joomlaupdate/config.xml
index 9259b7156e533..feb77e4a5abd4 100644
--- a/administrator/components/com_joomlaupdate/config.xml
+++ b/administrator/components/com_joomlaupdate/config.xml
@@ -19,7 +19,6 @@
 			<!--       All invalid/unsupported/obsolete options equated to default in code with 3.4.0 -->
 			<option value="default">COM_JOOMLAUPDATE_CONFIG_UPDATESOURCE_DEFAULT</option>
 			<option value="next">COM_JOOMLAUPDATE_CONFIG_UPDATESOURCE_NEXT</option>
-			<option value="testing">COM_JOOMLAUPDATE_CONFIG_UPDATESOURCE_TESTING</option>
 			<option value="custom">COM_JOOMLAUPDATE_CONFIG_UPDATESOURCE_CUSTOM</option>
 		</field>
 
@@ -29,7 +28,6 @@
 			label="COM_JOOMLAUPDATE_MINIMUM_STABILITY_LABEL"
 			description="COM_JOOMLAUPDATE_MINIMUM_STABILITY_DESC"
 			default="4"
-			showon="updatesource:testing[OR]updatesource:custom"
 			validate="options"
 			>
 			<option value="0">COM_JOOMLAUPDATE_MINIMUM_STABILITY_DEV</option>
@@ -41,11 +39,12 @@
 
 		<field
 			name="customurl"
-			type="text"
+			type="url"
 			label="COM_JOOMLAUPDATE_CONFIG_CUSTOMURL_LABEL"
 			default=""
 			length="50"
 			showon="updatesource:custom"
+			validate="url"
 		/>
 
 		<field
diff --git a/administrator/components/com_joomlaupdate/src/Model/UpdateModel.php b/administrator/components/com_joomlaupdate/src/Model/UpdateModel.php
index 9291cd9d14d2d..5b2bc74f08d0a 100644
--- a/administrator/components/com_joomlaupdate/src/Model/UpdateModel.php
+++ b/administrator/components/com_joomlaupdate/src/Model/UpdateModel.php
@@ -89,11 +89,6 @@ public function applyUpdateSite()
         $params = ComponentHelper::getParams('com_joomlaupdate');
 
         switch ($params->get('updatesource', 'default')) {
-            case 'testing':
-                // "Testing"
-                $updateURL = 'https://update.joomla.org/core/test/list_test.xml';
-                break;
-
             case 'custom':
                 // "Custom"
                 // @todo: check if the customurl is valid and not just "not empty".
@@ -115,6 +110,7 @@ public function applyUpdateSite()
                  * case 'lts':
                  * case 'sts': (It's shown as "Default" because that option does not exist any more)
                  * case 'nochange':
+                 * case 'testing':
                  */
                 $updateURL = 'https://update.joomla.org/cms/';
         }
@@ -173,13 +169,9 @@ public function refreshUpdates($force = false)
         }
 
         $updater               = Updater::getInstance();
-        $minimumStability      = Updater::STABILITY_STABLE;
         $comJoomlaupdateParams = ComponentHelper::getParams('com_joomlaupdate');
 
-        if (\in_array($comJoomlaupdateParams->get('updatesource', 'default'), ['testing', 'custom'])) {
-            $minimumStability = $comJoomlaupdateParams->get('minimum_stability', Updater::STABILITY_STABLE);
-        }
-
+        $minimumStability = $comJoomlaupdateParams->get('minimum_stability', Updater::STABILITY_STABLE);
         $reflection       = new \ReflectionObject($updater);
         $reflectionMethod = $reflection->getMethod('findUpdates');
         $methodParameters = $reflectionMethod->getParameters();
@@ -296,13 +288,9 @@ public function getUpdateInformation()
             return $this->updateInformation;
         }
 
-        $minimumStability      = Updater::STABILITY_STABLE;
         $comJoomlaupdateParams = ComponentHelper::getParams('com_joomlaupdate');
         $channel               = $comJoomlaupdateParams->get('updatesource', 'default');
-
-        if (\in_array($channel, ['testing', 'custom'])) {
-            $minimumStability = $comJoomlaupdateParams->get('minimum_stability', Updater::STABILITY_STABLE);
-        }
+        $minimumStability      = $comJoomlaupdateParams->get('minimum_stability', Updater::STABILITY_STABLE);
 
         $update = new Update();
 
diff --git a/administrator/components/com_joomlaupdate/src/View/Joomlaupdate/HtmlView.php b/administrator/components/com_joomlaupdate/src/View/Joomlaupdate/HtmlView.php
index 5147b60e20b6d..2426157f11968 100644
--- a/administrator/components/com_joomlaupdate/src/View/Joomlaupdate/HtmlView.php
+++ b/administrator/components/com_joomlaupdate/src/View/Joomlaupdate/HtmlView.php
@@ -239,12 +239,6 @@ public function display($tpl = null)
                 $this->updateSourceKey = Text::_('COM_JOOMLAUPDATE_CONFIG_UPDATESOURCE_NEXT');
                 break;
 
-            case 'testing':
-                // "Testing"
-                $this->langKey         = 'COM_JOOMLAUPDATE_VIEW_DEFAULT_UPDATES_INFO_TESTING';
-                $this->updateSourceKey = Text::_('COM_JOOMLAUPDATE_CONFIG_UPDATESOURCE_TESTING');
-                break;
-
             case 'custom':
                 // "Custom"
                 $this->langKey         = 'COM_JOOMLAUPDATE_VIEW_DEFAULT_UPDATES_INFO_CUSTOM';
@@ -259,6 +253,7 @@ public function display($tpl = null)
                  * case 'sts':
                  * case 'lts':
                  * case 'nochange':
+                 * case 'testing':
                  */
                 $this->langKey         = 'COM_JOOMLAUPDATE_VIEW_DEFAULT_UPDATES_INFO_DEFAULT';
                 $this->updateSourceKey = Text::_('COM_JOOMLAUPDATE_CONFIG_UPDATESOURCE_DEFAULT');
diff --git a/administrator/language/en-GB/com_joomlaupdate.ini b/administrator/language/en-GB/com_joomlaupdate.ini
index df136e0de89f4..5902c52891851 100644
--- a/administrator/language/en-GB/com_joomlaupdate.ini
+++ b/administrator/language/en-GB/com_joomlaupdate.ini
@@ -15,6 +15,7 @@ COM_JOOMLAUPDATE_CONFIG_UPDATESOURCE_CUSTOM_ERROR="The custom URL field is empty
 COM_JOOMLAUPDATE_CONFIG_UPDATESOURCE_DEFAULT="Default"
 COM_JOOMLAUPDATE_CONFIG_UPDATESOURCE_LABEL="Update Channel"
 COM_JOOMLAUPDATE_CONFIG_UPDATESOURCE_NEXT="Joomla Next"
+; Deprecated, will be removed with 6.0
 COM_JOOMLAUPDATE_CONFIG_UPDATESOURCE_TESTING="Testing"
 COM_JOOMLAUPDATE_CONFIG_VERSIONCHECK_DESC="Shows the checkbox in the pre–update check if any of the extensions installed on your site is potentially incompatible with the version of Joomla you are upgrading to. Note: the checkbox is displayed when upgrading to a new Joomla version family (minor or major version)."
 COM_JOOMLAUPDATE_CONFIG_VERSIONCHECK_LABEL="Potentially incompatible extensions checkbox"
diff --git a/libraries/src/Updater/Adapter/TufAdapter.php b/libraries/src/Updater/Adapter/TufAdapter.php
index 625ae512b55d0..d57ec0949cc1c 100644
--- a/libraries/src/Updater/Adapter/TufAdapter.php
+++ b/libraries/src/Updater/Adapter/TufAdapter.php
@@ -21,6 +21,7 @@
 use Joomla\CMS\TUF\TufFetcher;
 use Joomla\CMS\Updater\ConstraintChecker;
 use Joomla\CMS\Updater\UpdateAdapter;
+use Joomla\CMS\Updater\Updater;
 use Symfony\Component\OptionsResolver\OptionsResolver;
 use Tuf\Exception\MetadataException;
 
@@ -81,11 +82,11 @@ public function getUpdateTargets($options)
 
         $metaData = json_decode((string) $metaData, true);
 
-        if (!isset($metaData["signed"]["targets"])) {
+        if (!isset($metaData['signed']['targets'])) {
             return false;
         }
 
-        foreach ($metaData["signed"]["targets"] as $filename => $target) {
+        foreach ($metaData['signed']['targets'] as $filename => $target) {
             $version = $this->processTufTarget($filename, $target);
 
             if (!$version) {
@@ -108,7 +109,7 @@ public function getUpdateTargets($options)
             // Return the version as a match if either all constraints are matched
             // or "only" env related constraints fail - the later one is the existing behavior of the XML updater
             if (
-                $constraintChecker->check($version) === true
+                $constraintChecker->check($version, $options['minimum_stability'] ?? Updater::STABILITY_STABLE) === true
                 || !empty((array) $constraintChecker->getFailedEnvironmentConstraints())
             ) {
                 return [$version];
diff --git a/libraries/src/Updater/ConstraintChecker.php b/libraries/src/Updater/ConstraintChecker.php
index e7ae984ac8182..75f6f11ee952f 100644
--- a/libraries/src/Updater/ConstraintChecker.php
+++ b/libraries/src/Updater/ConstraintChecker.php
@@ -13,7 +13,6 @@
 \defined('_JEXEC') or die;
 // phpcs:enable PSR1.Files.SideEffects
 
-use Joomla\CMS\Component\ComponentHelper;
 use Joomla\CMS\Factory;
 use Joomla\CMS\Filter\InputFilter;
 use Joomla\CMS\Version;
@@ -50,13 +49,14 @@ public function __construct()
     /**
      * Checks whether the passed constraints are matched
      *
-     * @param array $candidate The provided constraints to be checked
+     * @param array $candidate         The provided constraints to be checked
+     * @param int   $minimumStability  The minimum stability required for updating
      *
      * @return  boolean
      *
      * @since   5.1.0
      */
-    public function check(array $candidate)
+    public function check(array $candidate, $minimumStability = Updater::STABILITY_STABLE)
     {
         if (!isset($candidate['targetplatform'])) {
             // targetplatform is required
@@ -89,7 +89,7 @@ public function check(array $candidate)
         // Check stability, assume true when not set
         if (
             isset($candidate['stability'])
-            && !$this->checkStability($candidate['stability'])
+            && !$this->checkStability($candidate['stability'], $minimumStability)
         ) {
             $result = false;
         }
@@ -208,23 +208,18 @@ protected function checkSupportedDatabases(array $supportedDatabases)
     /**
      * Check the stability
      *
-     * @param string $stability Stability to check
+     * @param string $stability         Stability to check
+     * @param int    $minimumStability  The minimum stability required for updating
      *
      * @return  boolean
      *
      * @since   5.1.0
      */
-    protected function checkStability(string $stability)
+    protected function checkStability(string $stability, $minimumStability = Updater::STABILITY_STABLE)
     {
-        $minimumStability = ComponentHelper::getParams('com_installer')->get('minimum_stability', Updater::STABILITY_STABLE);
-
         $stabilityInt = $this->stabilityToInteger($stability);
 
-        if (($stabilityInt < $minimumStability)) {
-            $this->failedEnvironmentConstraints->stability            = new \stdClass();
-            $this->failedEnvironmentConstraints->stability->required  = $stability;
-            $this->failedEnvironmentConstraints->stability->used      = $minimumStability;
-
+        if ($stabilityInt < $minimumStability) {
             return false;
         }
 
diff --git a/libraries/src/Updater/Update.php b/libraries/src/Updater/Update.php
index 76baad13cc1c9..ed4e42bddbeff 100644
--- a/libraries/src/Updater/Update.php
+++ b/libraries/src/Updater/Update.php
@@ -557,7 +557,7 @@ public function loadFromTuf(TufMetadata $metadataTable, string $url, $minimumSta
                 continue;
             }
 
-            if (!$constraintChecker->check($target['custom'])) {
+            if (!$constraintChecker->check($target['custom'], $minimumStability)) {
                 $this->otherUpdateInfo = $constraintChecker->getFailedEnvironmentConstraints();
 
                 continue;