SDL2 regression, all mouse clicks at wrong coordinates

I’m seeing an SDL2 regression where all mouse clicks are wildly off since the update: 2137027 – In Wayland mode, all SDL_MOUSEBUTTONDOWN coordinates are offset (SDL_MOUSEMOTION is fine)

However, in a minimal example as in this comment it’s all fine: Not getting a high DPI window despite SDL_WINDOW_ALLOW_HIGHDPI · Issue #6497 · libsdl-org/SDL · GitHub

I failed so far to boil it down to a more minimal breakage. I would highly appreciate guesses for involved subsystem settings or SDL2 hints or options so I can try to figure out how to actually make a working reproduction example since so far I utterly failed. It seems to be related to a DPI scale of not 1.0 in some way, but I don’t know for sure. The X11 video driver works fine (which might be due to not giving me a High-DPI window unlike the broken Wayland one, or who knows).