For me, Google video search, Google books (Internet Archive is good, but doesn’t always have the same stuff), Adobe InDesign (but in the process of learning LaTeX), and Typewise. As for the Google stuff, I liked Whoogle a lot, but almost all their instances seem to have been blocked or shut down. Also, apologies if this is repeating an earlier post.
Plex. I’m not sure if Jellyfin is foss, but if it is, I haven’t felt like converting my library. I’ve put a lot of work into making it just right.
Steam, obviously.
other than video games, I think that’s really it. I still use some others, like Spotify, but not primarily, I just like to have options.
Jellyfin is FOSS. You can by the way just install it and point it at your library to see if it recognises everything. It won’t change your file layout. If you have your movies named "title (year)“ and series in a folder format like “series title/season x/s0xe0x” (x being season and episode numbers), it should actually automatically recognise it all.
But I admit, if you have deviations from that you would need to correct those first and it seems from what I read that Plex is not as picky with that as Jellyfin is.
Misidentification is easy to fix in Jellyfin, with a couple clicks you can completely fix all metadata if it gets something wrong.
+1 for Plex. Basically perfect and so much more polished than JF (which I tried on three separate occasions to force myself to like).