It sounds like inkjets printers - subsidized cheap device, but full of DRM to lock you in. BUT! They are great if you are an advanced user and willing to buy 3rd party cartridges, mess with firmware, etc.
I wonder if all the mentioned issues can be fixed by using koreader.
I was hoping that Koreader would be a solution but after hacking my Kindle I found that Koreader would keep randomly locking up and require me to hard reboot the Kindle (wasting several minutes, and it would lose my place in the book). I ended up buying a used Nook for around $15, the online service is discontinued but you can still sideload books (including epubs).
I wonder if all the mentioned issues can be fixed by using koreader.
https://github.com/koreader/koreader/releases