Interesting about the pic rotation issue. There's generally two ways that apps handle photo rotation, they either rewrite the file with the new arrangement of pixels or they mark a piece of metadata inside the file to indicate the true orientation. It looks like somewhere in the software chain that orientation metadata is not being respected.
Lemmy is certainly still having growing pains, hopefully as more people use it and more people choose to develop for it these issues will work themselves out. Until then you might be able to get around that by putting the images though some sort of editing software. Likely most image editors will be able to fix the rotation issue and write the file out with the actual arrangement of pixels necessary to avoid gravity deifying doggos.