I'm not a good example since I was already using the compose plugin for a long time.
But the update was just that, an update. No issues:
My situation is the same, all my containers were already in openmediavault-compose. In fact Portainer no longer existed on my system.
If people had done this long ago the commotion would have been insignificant, but normally we are all animals of habit, for better or for worse.