After switching back to 4.3 it looks like access to the bases unaccessible in 4.4 is ok again. Looking at their date of creation I speculate that the affected bases might use seaf-server instead of dtable-storage-server, which was introduced in ver 3.0.
Is there any way to automatically migrate old seaf-server bases to dtable-storage-server bases? Or to re-activate backward-compatibility for seaf-server bases in 4.4?
Your assumption is completely right. Only bases that were created with version 2.x or 1.x are affected.
You find the necessary migration steps at: Extra Upgrade Notices - SeaTable Admin Manual.
I am sorry, that I didn’t update the page immediately this morning after we published the new version.