ReillyBrogan your environment has a lot of 2.4Ghz wireless interference?
No, that never occurred to me. The reason I started using the multi-device mouse and keyboard years ago is so that I wouldn't need other 2.4 GHz single-device peripherals and their dongles. And, as I mentioned, the Bluetooth versions've worked for years. And the keyboard is still working fine today (that's what I'm using right now.) It's something to think about, though.
Is there a way to clean the Bluetooth system to make sure that there's no stray config file somewhere that's causing my problems? Just going to Settings and telling the laptop to "forget" that device, and then reconnecting it, isn't helping. In the past I would have expected that to work. By the way, bluedevilglobalrc has re-appeared in my .config, after having been removed recently. It gets replaced automatically, apparently. I was under the impression it's an artifact of an ancient problem. Maybe a regression?
The only 2.4 GHz device in use now is the mouse I'm using because I can't get either of the Bluetooth mouses to connect now. And both the old Logitech mouse and the new Arteck mouse still gladly connect and work with the media computer across the room and the smartphone next to the laptop. Just not the Plasma laptop.