You can put G0 on the management VLAN that you are referring to. However, if you are using the guest portal/services then you need to dedicate an interface for that as well. You do that from "Administration > Web Portal Management ? Settings > General > Ports"
If you don't want to deal with this then you can put ISE on a general VLAN that is different than the management one that you are using and then restrict access to the management via:
"Administration > Admin Access > Settings > Access > IP Access" there you can define the IPs from which management is allowed. Perhaps there you can set your management subnet.
Hope this helps!
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