I have a Kobo, you can set it to “sideload mode” and you don’t need an account of any kind. It disables the store and all that and I never turn WiFi on so it’s completely offline.
I use Calibre, an amazing FOSS ebook manager, to sync my books to the Kobo.
Pretty much just download whatever from Anna’s Archive, throw it in Calibre and get it to fetch all the artwork and metadata if I want it and sync to the Kobo.
Calibre takes a little getting used to but it’s not too bad, it’s also extremely powerful once you learn more about it.
Shouldn’t have troubles since it’s 12th gen.
I have a Beelink with an 8th gen i5 that I bought a year or two ago and I love it. Runs Plex 24/7 right next to one of my tvs and the only time I hear it is if I’m in the same room when someone wakes it up to start a stream. The fan kicks in for 2-3 seconds then goes quiet.