I noticed that as I typed my post I hadn’t seen the screen go blank once. Then I posted it and read it over, and the screen turned black twice within a minute or so.
This makes me think it may have something to do with detecting inactivity, although I did disable anything that might dim or turn off my screen.
I saw a community post where someone had a similar issue on an Intel fw and Windows. They had to disable “Panel Self refresh” in the Intel Graphics Command Center.
This sounds related to me, but our setups are different since I’m on AMD and Ubuntu. I wonder if there is a similar setting for AMD graphics, but I don’t know where I’d find that.