There are some possibly helpful settings (thanks @Cradamy who adds that you have to trust Amazon to respect these settings),
- Settings -> Device Options -> Advanced Options -> Privacy
- It doesn’t tell that much what it does, but I seem to have it already disabled, but it asked me to disable Airplane Mode to see the status.
- Settings -> Device Options -> Advanced Options -> Home & Library -> Home Screen View (off)
- this fill show your library at first and at least not show you advertisements, but I am not sure how much this applies.
Edit: and now I immediately get a Kindle software update.
I have a Kobo, do you think I should worry too much about it? Is there something similar to a replacement of the OS with a FLOSS one for e-readers?
I don’t know about Kobo, but I jailbreaking Kindles is a thing