Just upgraded to 9.0.2 and found few hurdles to overcome:
Install of new python library “cffi” failed.
sudo apt-get install python3-dev
sudo apt-get install libffi-dev
Run upgrade script, restart, all work fine. Office preview does not work. In the upgrade instructions there is only mentioned that this is now done with a docker image. A hint that how this is installed would have been nice. But found it then in the manual under “office document previews” - there is a new chapter for 9.x.
Followed instruction until “docker-compose” - which failed with "service office-preview uses an undefined network ‘seafile-network’.
Any idea how to overcome this?