Open source is a license. What you're referring to is "source-available." You can't legally fork, redistribute, or contribute to it.
LinuxSBC
When you press a button on this revolutionary machine, it will automatically left click for you!
On GNOME, I like BlackBox, though Prompt looks promising once it's stable.
A combination of heaters and being mostly deployed in warmer environments, I'd assume.
They have an "Office Key" on some official keyboards. Pressing Office+L opens LinkedIn. The Office key is actually mapped to that long modifier shortcut.
Most of what you said applies to the Linux kernel too. It's good to have other options, but being popular does not mean something is bad.
.ovh domains are like $2/year, if that helps.
Also, KOReader adds a bunch of extra features and functionality.
Kindles are really hard to root. Use XDA Developers forum for this kind of thing. https://xdaforums.com/t/fire-hd-8-2018-only-unbrick-downgrade-unlock-root.3894256/, which is what that guide is based on, looks like it only works for the 2018 version and seems way more difficult and risky than most ROM installations. Also, that won't install Linux, just a different Android version.
Honestly, an actual ereader might work out better for you if that's all you plan to do.
It would be largely fine, but be careful. Being immutable, a lot of things that you would expect will work differently or not at all. I would not recommend it, but if you're in for a challenge, it's not bad.