My home lab doesn't have any metal VLANs available either. You've reminded me of a question I need to answer for myself too.
Do Harvester tagged networks require a VLAN metal switch, or is it a virtual-virtual-LAN?
I think it's the latter. I was confused at first because the VM I created on the tagged network showed a yellow pill like "DHCP failed", but then I learned that DHCP is not provided, and so there was no DHCP server on the same VLAN.
I will try it with a DHCP server to see if I can operate on the virtual Harvester-defined tagged network/VLAN.