as far as I see freetube is just written in html, css and Javascript, then all of that thrown into an Electron app. you can run these elements without Electron in any browser, it just won't have access to as many device features as the app does.
I've built a web version here from the source just to try it out. it's somewhat buggy but it does work
somewhat related, is there any way at all to enable high refresh rates while using resistFingerprinting, or something I could use instead of it? this is the only thing keeping me away from resistFingerprinting on Mull and Librewolf.