This is a plugin I found recently and really enjoy. It gives you the opportunity to redirect several webpages to alternatives. For example Youtube to FreeTube or Piped. If I search for youtube in Firefox, FreeTube automatically opens and shows me my feed. I like it, I use it, I can recommend it.
Yeah, that’s what I currently do. I’m just constantly annoyed how restricted I seem to be in Firefox mobile in general with add-ons. No scripting add-on, no redirect add-on, no User Agent add-on. I still run Firefox as my main on all devices, but using it on mobile is definitely my least favorite.
You can and have been able to install pretty much any add-on you want in the nightly and I guess beta versions, for a long time.
It’s not exactly convenient but it can be done.
https://www.androidpolice.com/install-add-on-extension-mozilla-firefox-android/