Blogpost about upgrading: https://owncloud.org/blog/introducing-owncloud-x/
General changes in this release: https://owncloud.org/changelog/#latest10.0
Please read those links carefully!!!
If you find another issue which should be in this FAQ, please write me a DM with a link to the problem/solution.
Common issues
Updates between multiple major versions and downgrades are unsupported.
Please see:
On every major upgrade it is recommended to do a full upgrade by deleting all files and fo…
The FAQ has an entry with an issue in github where people had quite some succes fixing this quickly by themselfs. Sorry for the oversight of this migration step.