Same issue here :( Has anyone found/heard of workarounds?

From the iOS 15 beta 8 notes, this may help: Using dispatch semaphores in an iOS app running in a device simulator on a Mac with Apple silicon running macOS 11 will cause the app to crash. (81783378) Workaround: In Xcode, select Product > Scheme > Edit Scheme, then deselect Run > Options > Queue Debugging > "Enable backtrace recording."

Seems to be fixed now

Same here, beta 5 seems to have corrected the issue.