Happens for me on two different Samsung Galaxy S7 (SM-G930F) with Android 8.0.0 and Minecraft 1.16.40. It used to work fine on these devices about two months ago. Local play does still work.
Playing on a server still works on my Samsung Galaxy Tab A with Android 8.1.0 though.
As mentioned in an earlier comment there is a Java exception triggered when the application tries to set landscape orientation for a transparent activity window. From logcat:
E AndroidRuntime: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mojang.minecraftpe/com.microsoft.xal.b
rowser.WebView}: java.lang.IllegalStateException: Only fullscreen opaque activities can request orientation
According to:
https://stackoverflow.com/questions/48072438/java-lang-illegalstateexception-only-fullscreen-opaque-activities-can-request-o
this appears to be a problem specific to Android 8.0 - API level 26. It used to work with older Android versions and works again with more recent versions. Google fixed something for later Android versions:
https://issuetracker.google.com/issues/68454482
However, I don't have the impression that this will be fixed on OS level for the numerous Android 8.0 devices out there, so it would be good if a workaround could be implemented in the app.