Firefox for Android
Does it happen on https://play.google.com/store/apps/details?id=org.mozilla.fenix ? If so, please grab a profile per https://profiler.firefox.com/docs/#/./guide-remote-profiling and file an issue over at https://github.com/mozilla-mobile/fenix/issues please.
Which niche add-on do you need? you could use IceRaven or Firefox Nightly
Appwrite - The Open Source Firebase alternative introduces iOS support. Appwrite is an open source backend server that helps you build native iOS applications much faster with realtime APIs for authentication, databases, files storage, cloud functions and much more!
Dark Reader Chrome and Firefox extension
Other extensions like uBlock also need it and if you're really suspicious you can check the source code on their GitHub.
Dark Reader Add-On Not Working
2 projects | reddit.com/r/firefox | 26 Jun 2022
Future Firefox Stable version 100
4 projects | reddit.com/r/firefox | 7 Apr 2022
Google experiments with non-WebKit Blink-based iOS browser
4 projects | reddit.com/r/apple | 4 Feb 2023
ZF9: Tons of bugs since Android 13 Update
1 project | reddit.com/r/zenfone | 4 Feb 2023
Firefox Android Requirement of add-on list in China
1 project | news.ycombinator.com | 4 Feb 2023