Spent a few nights this week, and most of the day today, writing a new GNOME App.
It lets you convert epubs to Kobo-formatted kepub files, and copies it directly onto your Kobo for you.
The code lives here: https://codeberg.org/nathandyer/Kepublicity
I'm going to request an app icon, then once that's ready I'll of course submit it to Flathub.

