Good news about page translation, Firefox is adding it, and it's all done locally too, no phoning home to their or somebody else's translation servers.

I wonder if there's an extension for Chromecast support? Might be worth looking into

For translation you can use this. Since you can use Google translation service as the backend(?), it works as good as Google translate atleast in my experience

For the time being I'm using TWP for translation. Seems to work flawlessly

I think libretranslate has a extension but I could be wrong

I'm using 2 extensions from the Firefox store, Simple Translate and Translate This Page. If one goes down, I use the other. Sometimes I use translate.yandex.ru as well.

only two things I will miss are chromecast and page translation.

You can use your phone to start the chromecasting, and translate.google.com lets you also put in a weblink to translate a whole page at once.