It’s all avenues to png or jpeg. The compression dialogue doesn’t appear and what you end up with is two files with the same name except one of them has a ~ after it. I ended up solving it by installing Debian on an old partition I haven’t run in a long time and the one difference is that I didn’t specify the same partition I usually have as home for my collection of operating systems. Probably a .Desktop file or something in that home messing things up. Gnome used to allow association of appimages with image file formats but the mimetype editor doesn’t exist in Debian 11. I resorted to using dolphin to create that association but something went wrong. I have spring cleaning to do.