I applied the fix detailed here: https://www.virtualmin.com/node/16227. After that it accepted the configuration check but when I ran an incremental backup, all the file sizes were zero. Ran it again this time not in the background and it thinks it succeeds, but the file sizes are still all zero.
I've tried to include the basics configuration wise, but I'm happy to provide more if needed. All updates, required by virtualmin or not have been installed, but otherwise, here's the details:
Virtualmin 3.82.gpl GPL Kernel 18.104.22.168-linode22 pbzip2 1.0.2-0
Backup configuration: Incremental backup of all servers to local directory, one file per server