Agreed I do pretty much the same.
bigfoot
I'm not sure what you're asking exactly, but the reason older and niche content is harder/slower to find sometimes is because there are fewer people out there sharing ("seeding") the files.
You could probably install a home server management software like TrueNAS Homearr or CasaOS on your Pi and just download the "apps" that way.
The large files are such better quality, though (if you care about such things and have a TV that allows you to appreciate the extra detail).
Torrenting will have everything you want within 48hrs (at the longest) as long as your tastes are relatively current and mainstream. If you are into older or more niche content you'll still likely need Criterion or Canopy etc.
I don't know why nobody has mentioned Anytype, which is excellent and just recently added collaboration.
because there’s not enough space on one M.2 slot to fit two M.2 ssds
It's not extremely uncommon for motherboards to put m.2 slots on the rear side these days, which opens up a lot of space.
A possible workaround: M.2 to PCIE adapters are pretty common. I could use one of those combined with a PCIE to multiple M.2. But this feels hacky and I don't love it.
I would love a radarr/sonarr style app but for YouTube with sponsorblock built in.
edit: sorry I missed where you said desktop app
It's not that hard. The easiest way to start is probably get qBittorrent, which has built-in search of several major torrent sites at once.