The Firefox browser now has a built-in page translator that works even without the Internet::Mozilla has announced the release of an update to its Firefox browser. In version number 118, users will find a significant innovation - a built-in translator
I just use brave browser when I must do casting. It works fine, you do have to enable it though. they call it “media router” or something like that in the settings. VLC also lets you cast to chromecast so there is a protocol for non-google apps, not sure why firefox never implemented it.