A Word about Apple's OS Betas
From our experience with previous OS updates, we feel safe to say that these betas are extraordinarily unstable and buggy. (…) Some public beta users reported synchronization outages and data loss that propagated to devices that did not even run the beta but were just connected via iCloud. (…) So, for the moment, we strongly advise against installing the public betas of iOS 13, iPadOS and macOS Catalina.
We have reports that iOS 13 Beta damaged the DEVONthink To Go data store by crashing in the night. And we’ve seen corrupted iCloud sync stores that might be related to the OS betas. So we second the Ulysses team’s recommendation.