First you need https://www.youtube.com/feeds/videos.xml?channel_id , and just paste the channel ID after it,that’s the link for RSS.
To get channel ID: visit the channel you wanna subscribe,then click more to view the full profile,scroll down and click share channel ,there will be a option Copy channel ID
I found it from a blog post from Taiwanese,his example: https://www.youtube.com/feeds/videos.xml?channel_id=UCVXstWyJeO6No3jYELxYrjg
WOW,I met FLOSS stuffs nearly 5~6 years ago and starting using Firefox and its variants,never heard that was officially supported by FF,it’s been so long,before my beginning.
There’s a Firefox extension called Livemarks that restores Firefox’s old RSS features. I started using it recently and I’m super happy with it!
What I using now is Liferea,I looked the Debian wiki of RSS and picked it.(I’m not familiar with terminal) I installed Livemarks then give it a try,simple and awesome.Thanks for sharing :)