I initially thought this was a problem with the beta, but may be more of a problem with the Google Play store.

After updating from 1.13.0.6 to 1.13.0.9, I was unable to launch the game. Tapping the icon would cause the screen to go black for a moment, then returned to the previous screen. The white loading screen never displayed. No troubleshooting on my end was able to resolve this, so I reluctantly left the beta and installed 1.12.0 from the store.

This morning, the 1.12.1 hotfix was available to me in the store. After taking the update, I was met with the exact same behavior - brief black screen, then back to my apps screen. I again tried clearing the cache, clearing the storage (world files, etc.), resetting the phone, powering off/on; no change. Only uninstalling Minecraft, and reinstalling from the 1.12.1 update resolved the issue.

I suppose for now I will rejoin the beta, turn off automatic updates, and back up all my game data before taking any update, in case uninstall/reinstall continues to be necessary.