I own an Onyx Boox Air, but sadly can’t recommend it as Onyx refuse to comply with the Linux kernel license and don’t publish their changes. Not only is this a dick move it means custom ROMs and hacking is not likely to happen.

Seconded, i love my Boox. it just runs android (with tweaks for e-Ink) and you can install what you want from the play store, it’s not locked down.

You can even install the Kindle app if you ever do want an Amazon ebook, works really well.

It’s also nice for using apps of various newspapers.

Plus the ones with a stylus make for a great notebook.

I wouldn’t recommend the color ones, it’s nice for comics but the colors just aren’t vivid and it’s not there yet in terms of quality.