Migration from OH2.5.11 to OH3

[LungBen (Benjamin)]

Regarding the migration of PaperUI config, maybe this is helpful for you:

OH2 Things gone missing in OH3

Renaming the JSONDB file to /var/lib/openhab/jsondb/org.openhab.core.thing.Thing.json and to rename all occurences of org.eclipse.smarthome.core in the file to org.openhab.core finally fixed this and made my OH2 things appear.

However, I have not tried the migration by myself yet.