It appears that https://github.com/flutter/engine/pull/42598 breaks the custom url paths of the example app.

[timmaffett]

It appears that flutter/engine#42598 must be breaking the URLs of the example app, as the engine now removes the query url before the example app sees it.

https://timmaffett.github.io/material_symbols_icons/?query=text_select_start&iconSize=48&fontType=universal&fill=0&weight=400&grade=0&opticalSize=48

this url should go to show the text_select_start icons (with other settings in query url) and the query url is now completely removed by the engine before it can be interpreted.

(It is possible it is not that engine PR flutter/engine#42598 that has caused this - but it is the only engine PR I recall recently and it seems a possible likely culprit. I will know more once I have a chance to debug this.)

[timmaffett]

I have fixed url query parameters being lost in the sample app. This was caused by the flutter framework throwing an exception on startup when it did not find a / route and then deleting all of the query parameters.
I save the query parameters at start of main() and then use (once) later.