Not sure what Solus' official POV is on these situations, but Shiftkey is available as a flatpak already.

After doing some testing (changing which packages/versions are installed, rebooting, and running usysconf run -f) I think I've narrowed it down to solaar 1.1.2-16 being installed that causes the issue. Only that version being installed presents the error, both with the prior and current versions of python-evdev installed.

Found that my motherboard's firmware was pretty out of date. I've updated it and that may have resolved the issue. I'll update this if I can replicate the issue in the next week or so (it's been happening just about daily prior to this).

Update: I am indeed seeing the sleeping issue again. Try to go to sleep, the monitors turn off, but the computer doesn't change power state and after a few seconds the monitors are on and I'm presented at the login screen.

Ok, so this is annoying. I literally had the issue last night and this morning, but after a forced power off and fresh boot, I'm able to to sleep and shutdown properly. Argh.

Yes, it is. Not near the PC right now but I can get you the specific error I’m seeing when attempting to sleep.

I was thinking there was something about FOSS vs proprietary going on here, so this makes sense. Thanks. I'll close this now.

I think there's some confusion here in how I presented the issue - on the fresh install I deleted both partitions (in GParted) and let the Solus installer completely reformat the drive. Is it possible this is still some sort of config issue if that's the case?

Wow, idiot me for not finding that before. Had to reboot after kernel update. Thanks!

This appears to be fixed by a reboot.