I'm still not able to get it working like it used to. I also tried setting the option to open the destination folder with double click completed torrents - still no dice. This isn't anything more than just terribly annoying, but I obviously use that option a lot and would like to get it working again.
The only changes I can think of aside from updating to 4.2.5 is that I had recently moved my default save location away from my home directory to a mounted directory with a lot more space. I've got rwx permissions on the mount and qbittorrent is running under the same account that owns the mounted directory. I honestly don't know if it stopped working when I change to the mount, but I can't say it didn't.
Also, after wiping the install on my CentOS box and still seeing it fail I installed v4.2.5 on one of my Fedora 32 systems - default settings - and Open Destination Folder works fine.
Any help would be greatly appreciated.
--ek