apparently (git bisected) 8bae343 (1) and 0249df9 (2) (i hope i did the bisect correct, bcs the (1) issue i only discovered while bisecting but not sure if i can reproduce it on the main code)
breaks "real" fullscreen for me completly.
Restoring the window sometimes uses a wrong resolution(1). Sometimes it thinks it's suddenly a desktop fullscreen window(2). Sometimes the viewport is just completly wrong(1). Sometimes the window doesn't even minimize at all (2) (for this issue i am not sure if its a third commit, but didnt really find anything). Also switching to desktop fullscreen sometimes make ddnet think its a window now, not fullscreen anymore(2)

KDE
x11
debian sid

tested with ddnet on vulkan

(tested against release-2.0.20 where i didnt have these issues)