Thanks MKX. If do have the second config. The problem was another brand device (Draytek router) that did not connect VLAN-tagged and same VLAN-untagged on the same interface properly.
My setup WAS complex … WAN and LAN both basically untagged streams … with a hAP ac2 on the WAN side cabling, that had to have an SSID of the LAN side as well.
And I started configuring with an Omnitik ac(for its switch chip only, using that HW), a RB260 switch, and a hAP ac2 on the WAN side, and a wAP ac on the LAN side.
WAN and LAN defined by the Draytek (RoaS). There are multiple LAN side VLAN’s (guest, iot, domotics, …)
Well starting Omnitik in switch method, learning the RB260 SwOS, and using the hAP ac2 in bridge method, all at the same time, was quite a challenging learning.experience.
I do understand the “pvid” / “Default VLAN id” now, I think. The SwOS has a nice interface to test those switch VLAN properties fast. The untagged WAN and LAN, and the mix of WAN VLAN’s and LAN VLAN’s could be added on top, could all be handled by the RB260 only. And as the switch method is almost identical, the QCA8337 in the Omnitik could do it as well.
I enjoyed the 141 posts in http://forum.mikrotik.com/t/using-routeros-to-vlan-your-network/126489/1