@stokerg, just uploaded two files to the link.
In v2,1 just opening the afpub file and trying to update, remove, add a new data source, I'm getting either crashes or the dialog above.
I've downgraded back to v2,0,4 and its working fine.
My files are technically on my Google Drive location on macOS 13.4, but I also tried moving the files to local file system avoiding Drive shares and nothing helped.
EDIT:
Describing step by step my issues:
1. open afpub file in Publisher, by double clicking file.
2. navigate to menu WINDOW -> Data Merge Manager window
3a. click the bin icon on the bottom of the dialog, Publisher 2 crashes
3b. repeat 1-2, click update data source if path was correct, Publisher can not find source data as above image