I think bypassing their gateway, that is - bringing your own router is the only way to do VLANs, because their gateway is very basic and doesn’t support VLANs at all.
You can do VLANs with their gateway but only IPv4, or you have to write custom scripts to ask for additional IPv6 delegations.
You can do VLANs with their gateway but only IPv4, or you have to write custom scripts to ask for additional IPv6 delegations.