Super!
Could you mark this as your solution (FAQ: How do I mark a solution?).
This will bump you to "level-1" and so you should be able to post images now.
And your solution taught me a little lesson about helping folks here and on other communities. When you wrote "I found other people with this problem in old posts, but no solution", I assumed you had seen the same posts I had linked to "R Graphics: Device 2 (ACTIVE)", in which some people had updated RStudio and resolved the issue.
I therefore didn't suggest the idea. But we probably should have started there.