I just got blinded twice in the pitch black darkness of my bedroom because Memmy randomly decided it's time for 2 seconds of light theme.
Seems to be triggered by switching between Apps.
Not only, sometimes the bottom menu flashes in light mode, sometimes just the top panel, sometimes the whole app. I will go now with the dark theme all the time to be safe.
Turning off the automatic light/dark switching fixed this for me. Having automatic switching turned on in the latest beta causes light mode for a few seconds when returning to the app in system dark mode.