... and no mods yet... hmmm
Just double-checking, but the image on the page before:
The littler window is from clicking the "Change high DPI settings" button, of course, and I have a computer where I had to use that top section, clicking on the "Use this setting to fix scaling problems..." tick box, and then on the "Use the DPI that's set for my main display:" and on the drop-down use "When I start this program". I have since been able to disable that section after a video card driver update (2x nVidia 980s).
I suppose when you open the "Properties" dialog there, you should revisit that first tab for "General", and make certain the "Attributes" section for "Read-only" is cleared fershure ferserttin...
You should not have any issues getting stock to run in WinVista through 11 with no problems. I have four computers with it on them, and one is VGA, one is DVI, one is HDMI & one is that video connect thingie... all have slightly different settings for that "Properties" "Compatibility" page.
Just happened to think - has the Ubisoft Connect updated, and "authorized" the license? That def has to be done with a UConnect version, similar to what the Steam version does.