My setup has 3 monitors and I am still using Windows 7.
I have also confirmed that this behavior occurs with Brave 1.11.104 and the latest Chrome. I have had this happen several times. When leaving a web page by backing out all of my monitors briefly go black and recover.
Can you try disabling Hardware Acceleration in settings to see if this resolves the issue?
You’ll find this in Settings --> Additional Settings --> System --> Hardware Acceleration
I have included a link to a specific site that causes this behavior. It does not happen on all sites. Although it doesn’t do this on my work computer. Hmmm
So seeing as this only happens on a certain site, you can reproduce on chrome, and it does not happen on your other computer. This does not seem to be Brave issues but more of an issue with your monitor/setup.