According to Logitech’s support page, the problem was caused by “an expired certificate” required for the apps to run.

Logitech users on macOS found themselves locked out of their mouse customizations yesterday after the company let a security certificate expire, breaking both its Logi Options+ and G HUB configuration ...

Editor's take: One feature that I'm glad to see return is the auto MagSpeed magnetic scroll wheel. When scrolling at normal speeds, it affords the same clicky feedback you'd experience with most any ...