[Metricon]

I've been using the "Brief" addon for Firefox since the built in RSS reader was removed and it's worked very well for years:

https://addons.mozilla.org/en-US/firefox/addon/brief/

Source: https://github.com/brief-rss/brief

Also, for those not aware, Youtube still supports RSS feeds (for those without Google accounts) in the format of:

https://www.youtube.com/feeds/videos.xml?channel_id={Channel Id}