Just noticed that the 2 new directories were created Sep 23, 2023 and Sep 24, 2023. This was after I jumped to v1.65.0 (first time getting the refactored B2 code), but before I switched to deadlock fix branch.
The config hasn't been changed since 2019.
$ stat .config/rclone/rclone.conf
Access: 2023-09-25 23:37:14.503939021 -0400
Modify: 2019-06-29 14:31:50.273889934 -0400
Change: 2019-06-29 14:31:50.273889934 -0400
Birth: 2019-06-27 00:53:52.983508710 -0400
I believe it uses its own digest / fingerprint value that it adds to the remote name. Remember seeing it in code a while ago.
I checked, and unfortunately journalctl in my case doesn't go back to Sep 23/24 already, probably because I enabled DEBUG mode for another issue and it since rotated logs due to increased volume.
Hm, could this issue happen if data on B2 remote was modified manually? Is that what the random string on the directory name represents — a digest of complete remote state?