I have never imported from phpbb.
But what I can say is I have had success importing other forums to a older UBB forum then upgrading to a newer UBB.
The importers are quite old.They were developed prior to mysqli and the 7.7x ubb series.
Try this:
You will need to downgrade your php to no higher than php 5.6
Install say UBB 7.5.7 or 7.6
It has a importers folder in the forum folder.
Place the phpbb importer in that folder and run it.
It will ask for login info to your phpbb forum.
If successful then upgrade UBB in one step to ubb7.7.5
Then you can change php to php 7.x
Last edited by Ruben; 02/18/2021 3:24 PM. Reason: Corrected typo
