Updater did not work for me.
First it complained about the folder “assets” being present, then about not being able to write to the “updater” folder. My permissions on ALL folders were set as suggested per https://docs.nextcloud.com/server/10.0/admin_manual/installation/installation_wizard.html#strong-perms-label
Apparently these settings are not compatible with the updater. Did a manual (backup &) update as per a modified version of the script suggested here: Shell script for backup and upgrade (nextcloud or owncloud)