Confirmed on Android 11 – Affects Realms and servers (can't test direct connect to a friend's world)
Attempted fixes:
Check 'Use Cellular Data' didn't get unset during update: No, still selected
Unset 'Use Cellular Data': connects fine on wifi
Reset 'Use Cellular Data': can't connect
Force stop Minecraft: can't connect
Clear cache: can't connect
I did not clear all data or uninstall and re-install for risk of world loss.
I just encountered this trying to update from v1.11.0 on the current Pixelbook. Minecraft v1.11.0 still works, in that I can connect to my realm. Very frustrating.
Video demonstrating reproduction steps can be seen here: https://youtu.be/Fg9NyZh0aHw