You're on a newer network architecture called DSA. The default LAN bridge interface is br-lan. Once you start tagging it it would turn to br-lan.1 e.g.
Notation for single ports is e.g. lan1:u* for lan1 port in the default untagged VLAN, lan2:t for lan2 tagged in a VLAN.
This script should be enough to set up a basic tagged LAN and expose the VLAN entries in LuCI. From there you should be able to set it up through LuCI.