The thing with fullscreen and certain resolutions different from your desktop usual resolution on Linux is that there is more than one way to switch resolutions, and things can go wrong when apps expect different versions of stuff.
xrandr -s 0
in a terminal also fixes this (this resets default display device resolution to maximum).
Because of this reason, SDL2 and most games allow borderless window fullscreen, and if your game is in a window, you can often just press ctrl+alt+f or Meta+f to switch it to something that behaves almost exactly like a fullscreen app. Check your window manager settings for "Toggle fullscreen" shortcuts.