That is your default or you mean that being the default by the OS? For the latter all DSA ports are in untag state, check with bridge v, e.g. prints
port vlan ids
lan0 1 PVID Egress Untagged
- untag state (one VID per each port only)
bridge v a dev lan1 vid 8 pvid untagged - tag state
bridge v a dev lan1 vid 8 tagged, or
bridge v a dev lan1 vid 8 pvid tagged
similar operation for a bridge port exchange the device name, e.g. dev lan1 with dev br-LAN2_IOT.