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.
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.)