This is currently happening to me on Windows 10: Inkscape 0.92.3 (2405546, 2018-03-11) Didn't happen on 0.91
Everytime I set the Display Units to mm, save, close and reopen file, it's always px. I'm doing this for laser cutting as well.
I had this problem on Ubuntu 18.04 as well, but I moved over to the Windows OS because it handles DXF import files better without crashing. But this px to mm has been annoying.
This is currently happening to me on Windows 10: Inkscape 0.92.3 (2405546, 2018-03-11) Didn't happen on 0.91
Everytime I set the Display Units to mm, save, close and reopen file, it's always px. I'm doing this for laser cutting as well.
I had this problem on Ubuntu 18.04 as well, but I moved over to the Windows OS because it handles DXF import files better without crashing. But this px to mm has been annoying.