Title was indeed promising but unfortunately thread was containing not much useful information.
I've read that DSA and Swconfig are mutually exclusive. In my case swconfig being enabled, DSA seemed irrelevant, and indeed, I was not able to create vlans using the device configuration.
The confusing part is that in the current state of OpenWRT, not all networks are created equal, like the asymmetry between wired and wireless:
- if you want to bridge 2 LAN ports, you just create a bridge and select the 2 devices you want to bridge
- if you want to bridge a LAN port with a wireless radio you need to apply a different procedure and change tabs...
- etc.