Goes well with their equally horrible hardware.
Time to realise the Mac era is over. Sadly. It hasn’t been a focus for the company in over half a decade.
This is using Catalyst, right? UIKeyCommand is a UIKit name, not an AppKit one. And Catalyst doesn't exist prior to Catalina. They've added a whole other (temporary?) operating system. It's perhaps not surprising this has a lot of bugs. Classic wasn't perfect, either.
That won't help you escape Catalyst bugs, except that you won't be able to run any Catalyst apps. But you can just stop running Catalyst apps, now, without reinstalling your OS.
I managed to do it during the beta. Since Catalina installs the OS on a separate partition inside an APFS container, I wiped the OS partition, then booted into one of the recovery modes (there are 3, I think) to reinstall Mojave on the partition containing my data. No data had to be wiped, and most kept working. Music library won’t work with iTunes but I got around that with Apple Music iCloud Library. A few other things won’t work, like Mojave Reminders won’t sync with iOS 13, but otherwise it wasn’t so bad. Think I had to reinstall Homebrew and Node and that was about it. After that I just removed the now-blank partition that formerly housed Catalina and renamed my data partition back to its regular name.
Unfortunately I do not recall which recovery mode I booted into. I tried a few, each offering a different OS to install. One would reinstall the current OS, one would reinstall the version that shipped on the Mac, and one would reinstall the current public build, I think. Wish I had a better recollection of which it was, but since Mojave is no longer the latest public build it may be moot. If you have the Mojave installer downloaded you might be able to just install it right on the data partition and wipe the Catalina OS partition afterwards.
Whatever you do, have a full backup before you even think about starting just in case, of course.