Hi @Anonymous ,
You could use this graphy api to list all groups a user belongs to:
https://graph.microsoft.com/v1.0/users/{UserID or User Email}/transitiveMemberOf/microsoft.graph.group?$count=true
I've made a test for your reference:
1\Create a flow

2\Insert the flow into the app

3\Add a text input control and set it's OnChange property to:
Set(GroupsBelongsTo,Bof0804_1.Run(Self.Text).groups)
4\Add a datatable and set it's Items preoperty to:
AddColumns(GroupTalbe,"IsBelongTo",ThisRecord.GroupID in GroupsBelongsTo)
When we fill in the user to be found in the text box, the table will show which group he belongs to and which group he does not belong to

Best Regards,
Bof