After updating to Affinity Photo 1.9 (Windows 10), I couldn't open any new or existing files until I unchecked Edit - Preferences - Performance: Hardware Acceleration. After that, it worked fine.
Yesterday I installed AP 1.9.1 and re-enabled Hardware Acceleration out of curiosity, but run into the same issues: stuck while opening, no way gracefully exiting the program. Screenshots attached.
Disabling HA solved it again.
Lately, I've been using Affinity Designer 1.9 (now 1.9.1) a lot. Never had a problem although HA has always been enabled! So, this should rule out any driver versions or Win 10 settings.
Maybe my observation helps troubleshooting?