You're doing the Lord's Work. Keep it up, please and ty!
NexusMods is working on their new post-vortex mod client, which does have Linux support. It can be found here on github.
That's stupid. Nothing stops you from just installing regular Ubuntu if you love snaps so much.
There's Librera FD, on F-droid. It's the open source version of Librera on the google play store. I believe it strips out the google api/cloud stuff, but its db /reading status/etc are all easily synced via Nextcloud (which is what I do). The only real negative I've found with it is that it's search for text in books is slow compared to more popular reading apps like Moon+ Reader.
This must be some weird American thing. I've gotten pixels on contract before in my country and I can OEM unlock and flash them no issue. If you don't pay the cell carrier will just blacklist the IMEI. They don't lock down the device itself.
Aegis is for Android, Ravio is an iOS app.
It is still possible if you have an old enough Kindle. I have a 1st gen paperwhite and can just connect it via USB to my PC and pull books off the kindle with Calibre and then remove the DRM.
Though if you're wanting to remove DRM from Kindle Unlimited books, you'll have to actually edit the DeDRM plugin code, as by default its set to not let it be run on KU books.
Have you tried adding it to Steam as a non-steam game and then forcing compatibility for it to proton experimental in Steam?
Basically any Fossil / Skagen (they're the same thing) Hybrid (meaning e-ink) watch will work with Gadgetbridge. I personally have the Fossil Machine Gen 6 Hybrid which works great. Ignore the 'Alexa' bit, that does nothing via Gadgetbridge (and in fact you can just flat out remove that 'app' in the GB app). Heart Rate and Message/Notification/Call control functions all work fine. Step tracking works, but sleep tracking does not (Fossil doesn't have it done on the watch, it's done in their app, so until/unless GB replicates that functionality it won't work).
I use a Fossil Hybrid watch with gadget bridge. Works really well, though one caveat is that while you can read and dismiss messages on the watch, you can't reply from it. This isn't a problem for my use case, but YMMV. The couple weeks of battery life is a great plus, though. (E-ink screen)
Uninstalling my primary browser isn't really a practical solution, what am I supposed to use, Chrome? How about fixing the version they're shipping? Or should I be looking somewhere other than F-Droid for Android Firefox?