When I switch to discord, or whatever app I have open on my second monitor, the display flickers.

Then when I switch back to minecraft, that display flickers.

Seem to be having the same issue with the v2.0.0 alpha build in 1.18. Tried a fresh 1.18 instance with only Fabric + Borderless Mining to rule out compatibility issue with Sodium/Iris or other mods.

What graphics hardware do you have? I know AMD drivers don't handle borderless fullscreen as well, and from what I've seen #19 doesn't help, though I am working on a solution.

Ahh, yeah I have an AMD RX 5600 XT.

I mean, would be nice, but I can live with it if it be can't be fixed. Definitely better than having the game window straight up disappear when switching to the other monitor.

Please try the testing build in #19.

Same issue here with 6900xt AMD 22Q2 professional/enterprise drivers

I know AMD drivers don't handle borderless fullscreen as well

I tested 2.0.0 with 9600M GT as well, flickering is still here.

This is because the game is actually un-fullscreening from regular fullscreen exclusive into an actual borderless window. Whilst in-game, you're actually just using regular fullscreen, which is good for performance and input latency.

It shouldn't really be dependant on your graphics card, it's just how fullscreen exclusive works.