Did you try su -l?

Gah crap.

Good, leave so they replace you

Ubuntu. Package organization is annoying, versions are out of date, managing multiple versions isn’t consistent, and distro upgrades always have unintended consequences. Often ones that aren’t easy to figure out. Their reputation for being beginner friendly should have died around a decade ago.

Second on kobo, sure the OS is proprietary, but it’s good enough that I forget. And as the previous comment said, you can install third party reader software. I like koreader, it pretty much replaces the entire UI of the device