Is Kobo the best non-Amazon e-ink reader out there?
I wouldn’t use it.
I don’t love using Chinese software that I’ve seen claimed doesn’t follow the GPL, but anything that isn’t Android is way too much of a downgrade for me to tolerate.
I use a Boox go color 7 and a Boox max. I’m waiting impatiently for them to manage a full 13" color version. Android makes it easier to get content from multiple sources and lets me use reader apps that give much more control over navigating content and how it’s displayed, and as a bonus I can occasionally play with code on it.
There are other options that run Android as well, but I prefer the tools Boox provides for managing the display, and the go specifically having page turn buttons is great for my pocket reader.