Discovered you can force dark mode for non-native apps. If you type this into terminal:
'defaults write com.cockos.reaper NSRequiresAquaSystemAppearance 0'
To change back replace the 0 with a 1.
Makes all tops of windows dark (which can't be done via themes), system messages (like save this project) and right-click menus.
There's a few bugs at the moment with the latest version of reaper.
Playhead doesn't display properly, seems to disappear intermittently. Not sure if this is just on my theme. That's a deal breaker for me, really want that to work in future.
Start up splash animation bugs out a little. Can swap in a custom image as a workaround (also seems to break PNG transparency)
The FX/plugin window looks bad and can't seem to change that via the theme. I expected it to follow the other windows colours. The FX window does seem to run on its own menu system. Also the wet/dry knob doesn't go dark.
Info from this post -
https://www.reddit.com/r/apple/comme..._applications/