I use NextCloud as alternative to Google Photos. My smartphone sends pictures over OpenVPN to my NextCloud instance. However for over a year Android application has been showing notification that server version is outdated, and from time to time automatic upload do not work. So I decided that it is the time to do an upgrade. It did not work well:

I tried to run upgrade using UI. It got stuck in various places, and finally I got this:

But there is much simpler option. Install fresh copy of NextCloud. I prefer using VM ISO (https://www.turnkeylinux.org/nextcloud) instead of LXC containers. I feel that sometimes LXC container draws too much constrains and limitations, such as quircky backups, kernel features etc. Once you have clean install copy data from original location to /var/www/nextcloud-data/ and run the following command:

sudo -u www-data php occ files:scan --all

Be sure to install sudo first (apt install sudo). That’s all. I use only NextCloud as automatic photos and videos upload co my case is quite simple. If you use various different integrations, calendars, mail etc, then your migration scenario is much more complicated.

Please note that I tried fixing all these upgrade problems with permissions, missing files etc, but after and hour it got permanently stuck, so I decided to go with easy way.