I will probably end up with a different solution
I teste FileRun in a LAMP app (after reading @scooke reply here) and it does exactly what I need without all the added bloat and unpolished UI of Nextcloud.
ā It sorts pictures by date taken
ā Has a better UI than NextCloud (personal opinion)
ā It is a lot faster in previewing images
ā Works with the Nextcloud desktop and Android client (or any other app that supports webdav)
ā Can organize photos in albums and collections (I am not really interested in this, but it's a nice to have)
I hope that it will officially come to Cloudron at some point.