I use newsboat too, just never considered using it for YouTube
An alias wrapper immediately adds flags for medium quality (highest is often massive file size), subtitles, and sponsorblock (cuts out mentions of sponsirs via sponsorblock api). I also have similar aliases for high quality vids if I want them and also just extract audio for music. I watch/listen using mpv.
I actually do the same thing
On mobile I use GrapheneOS and Libretube
Fucking based, I use the same stuff
I'll try out something similar to your setup, but I will use my self-hosted FreshRSS server that connects to my newsboat as well as my Invidious instance. But keeping my subscriptions in my self-hosted Piped or Invidious is fine as well.