Yes, for the ones I've owned rooting is very easy. KOReader and Plato are both popular (amongst the community of eReader rooting people) alternatives to the OEM software.

The article's update points out that it switches to a modern renderer if you rename .epub to .kepub.epub, which seems like a dumb way to handle that rather than a DRM existence/version check, but that's not entirely unusual for backwards compatibility support shenanigans.

(Others point out that Calibre automatically will rename epub files to .kepub.epub for you if you use it to manage a Kobo library. It's just manually copying files to Kobo where you need to remember to do it yourself if you have a Kobo.)

It runs a standard linux and mounts as external storage when connected over USB. No need to "root" at all.