I failed to check the version had actually changed in the modules page. That indeed was the same problem, was stuck on beta1 despite having attempted the upgrade. Now behaving as expected.
For anyone else following along, MQTT Engine configuration is retained despite the uninstallation of Engine. So at least it’s not going to result in lost config if this needs to happen in a production environment, but hopefully root cause of whatever is responsible for upgrading modules to not work can be addressed before exiting beta.
Thanks for the help. Good job identifying that, could have wasted a bunch of time not realising the new version hadn’t actually applied.