Sorry for late reply. Yes, the IDE is working on that computer. Just the richtext does not change its background color when in dark mode. I just checked for dark mode and set it from code and all was fine.
The richtext control changes the text color (in my case, black to white) in dark mode automatically, but not the background, which stays white. Therefore, you don't see the text. Just that.
This is worth investigation. Do you think you could try to provide a testcase? (Simple minimal example (as package) that demontrates the problem?)