Actually, it looks like PeerVue for Roku is what you're looking for.
PeerVue appears to be dead / abandoned
Yeah, but it's the only software project I've found so far that matches your description. Theoretically, it might work, although it could probably be forked and updated to support any potential API changes.
So, they already have an Android app that's pretty decent, and could be adapted to a TV form factor.
https://framagit.org/framasoft/peertube/mobile-application/
There's also a Kodi integration, but I'm not aware of how well it's been maintained. Given the amount of things Kodi can run on, that might be a good starting point.
NewPipe/PipePipe supports both YouTube and PeerTube.
Is it available for ROKU?
Don't know, doubt it. Mentioned it because "Other smart TV platforms".
FWIW, if you have a Fire TV, Peertube seems to work in Silk. Well, mostly. I couldn't get thumbnails to play, but the video itself ran smoothly on its own page.
I don't use Fire TV.
I use ROKU.
And I have a SAMSUNG, which I already have the app installed on.
I'm not sure about Roku. I brought up the Fire Stick because that's what I have, and you were asking about other streaming platforms, too. I suppose you could try loading something on your TV's browser and see if it works? It'd probably be super clunky but it would do until there's a dedicated app.
Peertube
A free software to take back control of your videos
Peertube is an open, federated alternative to Youtube without advertising or tracking. On this site, you can find a good Peertube instance, with good rules, good moderation and most importantly a friendly community.