Updating from 11.0.1 to literally anything when using snap

Hello there!

So I’ve just flashed the Ubuntu Server 16.04 image with the nextcloud snap from here and am now trying to update. The thing is, the built-in updater does not work due to lack of writing permissions (a topic that has been covered extensively in this forum). Since I am using the snap setup, however, I couldn’t find a way to apply the chown-fix described here in a working fashion. Refreshing the snap also doesn’t work because Nextcloud will then try to upgrade to version 12 and inevitably fail because skipping versions is not supported. The fix for that also does not seem to work for nextcloud snap since there is no “one nextcloud directory” but rather multiple different locations.
I am now genuinely at a loss and have already poured 5 hours into trying to find a solution without being successful. I’d be very happy if somebody knew a solution to the problem.
Thanks in advance for your help!