Hello.
Thanks for your questions:
- the group type seems to have no impact on the app behavior. Regardless of being shared update or not, i can reproduce the behavior for all groups (again, i am an Org Admin so i've tested groups I own, groups i don't own, collaboration groups, shared update groups, plain-ol-vanilla groups, etc. The behavior is the same.)
- there isn't an error message - its just that the Save button in the Change Owner popup is never enabled. Using chrome dev tools, I checked the response whenever a user name is selected in the popup, and a big load of json is returned, including a list of privileges that includes 'portal:user:receiveItem'
- subscription is not suspended. Everything else about AGOL seems to work fine - including being able to change owner of the group via python script.
- the behavior is the same in Chrome and Edge