I don't know if this is related, but I have a similar issue with the Windows 10 Settings app not loading, combined with another issue, with some steps to reproduce:
Open "Edit Style" > Window Title Bar > Advanced Properties > Override Font = Enabled > Open font picker in next row > Scroll through fonts > *crash*
For me, Curtains settings app will crash out with no error part way through scrolling. I can open the settings app again and make changes, but this consistently happens.
If I type the name of the font into the top left box of the picker, this tends NOT to crash out.
This ties in to silveriovicentejr 's report in that once Curtains crashes out via the steps above, the Windows settings app will no longer open.
Rebooting the system fixes the settings no launching issue until I repeat the process. I don't think I have any fonts beyond the Windows 10 stock installed.
Full relevant config: Windows 10 20H1, Curtains, Startisback, Rainmeter, MacType and PowerToys all running. No issues with any of these other than this one. I will try and turn these off one by one and see if it stops Curtains falling over, and will post if anything develops.