Sounds like setting up a template board with the desired groups might be suitable as a workaround. Happy to walk you through this on a call together or further discuss the requirements and help find the best approach if you’d find it helpful
Unfortunately, I don’t believe that will work in this case.
Board A is grouped by clients, board A is organizing “project sites” [items].
Board B is grouped by client organizing approved “subcontractors” [items].
Board A is a Master List and would have groups added on a regular basis.
Goal: When a new group (Client) is added to Board A, the same group (client) would be automatically added to Board B.