I installed Publisher 1.8.5 on Windows 10 with 2H20 update today. The splash screen appears but the next screen is blank and I can't continue with the first run. I attach a screenshot.
I guess it could be connected to the known issue listed here in the FAQs: [KNOWN ISSUE] Affinity apps no longer start after installing the Windows 10 October 2020 (20H2) update - Frequently Asked Questions [FAQ] - Affinity | Forum (serif.com)
I also tried Affinity Publisher Beta - 1.9.0.874 but that behaves the same.