WRT32x not create switch (mvebu uses now DSA instead of swconfig)

It was changed to "switchless" DSA approach in last week by @adrianschmutzler. He may be able to help you.

I have not seen any real docs about VLAN config for DSA so far, and only little relevant discussion here:

Forum search mgiht provide more hints on what is the correct approach with DSA.
https://forum.openwrt.org/search?q=dsa%20vlan

Developer mailing list:
http://lists.infradead.org/pipermail/openwrt-devel/2020-June/023774.html
http://lists.infradead.org/pipermail/openwrt-devel/2020-June/023812.html