Occasionally I've seen posts with unrecognizable image attachments. The posters always claimed that they did nothing wrong - if they noticed at all.
I now managed to reproduce the problem but don't know how to fix it.
Below are 3 images: The logo mark dowloaded from the this server and 2 screenshots in JPG and PNG taken with mtPaint default setting.
Should be no problem to attach them,right? Let's see:
What I do know is that this is a browser problem. I'm currently posting with Firefox 102.9.0esr. This is the browser preinstalled in @dimkr's Vanilla Dpup 9.3.13
I have the same issue with LibreWolf 110.0