These days, whenever a new gadget comes up, my first reaction has become "I wonder how they try to screw you into a SaaS later".
Edit: I think people may have the impression this is like Android where the process is "ok, first reboot, hold all the buttons but not that one button and then unlock root, then flash the rom with a custom version of the OS from this sketchy site and ... bam! You're in control now"
Actually it's like: sign into wifi on the device. It's now running an ssh server available on your network. The password to log in as root is in the settings. You can ssh in right then and write a bash script to do what you want.
I was really considering getting one, but I think the bigger issue for me is the LiPo battery. You can’t take the thing apart without a heat gun because it’s held together with adhesive, so in a few years when the battery doesn’t hold a charge, you have an expensive paperweight. I would pay a premium for a thicker device that used normal screws so that consumables such as the battery can be replaced easily.
(Many devices these days are similar, so it’s not only ReMarkable doing this.)
Regarding the Nextcloud's sync functionality on iOS, though: Does it support two-way sync? And do note-taking apps like Notability support it, too? Last time I checked, my impression had been that none of them does – which is a deal breaker for me, given that I'm a heavy user of Syncthing and have really gotten used to its instant two-way syncing functionality to keep all my devices up-to-date.
The problem is this is more of an import/export workflow rather than seamless syncing. I use it a lot while drawing, the files are all stored internally to the app but when I’m done I save the result to Nextcloud.
It would be nice to have apps automatically save everything there but I think Apple wants to avoid having these remote storage setups as primary storage so your device is still usable with no network connection.
Hopefully this doesn't change, because it's really a pain to put things on the tablet without using their app.
Have you tried Syncthing[0, 1]? I'm actually considering buying a ReMarkable 2 right now and the fact that Syncthing seems to be working on it is playing a major role in my decision process.