How to VLAN for separate interfaces on combined router / AP / Switch


currently I use my Mi Router 3G with 21.0.2 as central router (for 2 remote APs )and AP. Now I try to configure a separate (VLAN) interface to have a guest WLAN and to distribute this over the integrated switch to the other APs.
I'mcommon with VLAN, Routing etc., but not with the new openWRT implementation.

I can add an Interfaces, VLAN 10 for guests prepared:

But changing the bridge interface from VLAN-unaware to VLAN always breaks my connection.

(I hope the screenshots are attached).

Any ideas, where I have the flaw in my thinking?

You do need to change the lan interface device from br-lan to br-lan.1 at the same time.

yes, obviously I forgot this.

I added another tagged device br.1, and changed the interface.

still not working...
How can I now find what's missing?

Unintentionally I tested further (rollback did not work;))
Configuration IS working on the wired Ethernet (other APs). But on the local wireless network I don't get DHCP address, which is also connected to the same "LAN".