So I have Carla working as a standalone, and with the MTPDK-2.0.9-VST-64bit-Win-FULL drumkit that I'm testing it with, it's all working just fine.
I can also see the Carla VSTs -- Carla-Rack, Carla-Patchbay and so on -- from the input FX and FX buttons in Reaper. The problem is that when I try to load any of them, instead of getting the Carla GUI like I'm supposed to (and like this guy does at around the 4:55 minute mark --
https://www.youtube.com/watch?v=KuO39baiBGw ), I just get to see a bunch of broken/overlapping Reaper windows with no sign of the carla GUI. Hitting the UI button (top right corner) gets me to a bank of unlabeled sliders, and hitting the UI button again toggles the amount of grey space to the right of the sliders.
In Reaper preferences/plugin/VST, 'Default VST to generic UI (instead of plugin UI)' is unchecked, but it doesn't seem to make any difference either way.
I'm using reaper v6.12c and carla 2.2.0-beta1 under Ubuntu 20.04 with gnome.
Anyone have any ideas how to get this puppy working??!