This issue refers to Trello (I cannot find a community board for this product so was hoping the issue is similar with Confluence)
I cannot deactivate any accounts as I get the error message below, yet these accounts are disabled/deactivated in GSuite - they are in an OU that has no access to Trello.
Account is managed by your identity provider
This account is the only member of one or more boards. There will be no way to access those boards until their account is reactivated.