I’m working together with @sbernhard at the same discourse instance (2.7.12) - as a moderator, I’m not a developer/admin. Until now, the “500 Internal Server Error” appeared at accounts with moderation rights. Normal users seemingly don’t get this error - they can access “Upcoming events” at the same moment, accounts with moderation rights is shown the error (at least, we didn’t receive other error reports yet).
As moderator, I get the error with Firefox 100, Edge 101 and up to date Chromium 101 on Windows 10 Pro, but as well on Ubuntu with Firefox. With a standard user account I don’t get the error on the same systems.