I recently built an AMD-only PC, and whenever I click between my secondary monitor and my main monitor with a fullscreen game, the game flashes black for a second. I also can't get the Windows menu on top of the game itself while it's selected, which is something I was able to do with my laptop that used an Nvidia graphics card. It almost feels like my GPU, a RX 7900 XT, is doing something to fullscreen / borderless fullscreen games, which stops me from seeing things on top of the game, and which stops the game from running in borderless fullscreen as it would normally.
For testing, I've been using Roblox, the same issue doesn't apply to osu! lazer though. It applies even if I try to use Borderless Gaming on Roblox instead of just pressing F11 for in-game fullscreen.