EdgeRouter X (ER-X) with OpenWrt 21.02.1 and "Enabling vlan filtering"

Hello, I have an EdgeRouter X (ER-X) [ Architecture MediaTek MT7621] with OpenWrt 21.02.1 and unfortunately I can't manage to enable VLAN support on the switch. With OpenWrt 19.07.8 and the old switch config (swconfig) everything worked great with the new switch config (dsa) it does not work.

I also tried to change the config manually under /etc/config/network, but after a reboot the switch is not reachable anymore and has to be reset.

Has anyone managed to get the ER-X working with DSA VLAN support?

Howto DSA: https://openwrt.org/docs/guide-user/network/dsa/dsa-mini-tutorial

I just installed OpenWrt (SNAPSHOT) on a Netgear GS308T v1 (Architecture RTL8380/realtek).
On this device DSA works as expected, you can create vlans without problme.
So obviously there must be a problem with the ER-X and DSA.