Thank you @atownlede !
Your hints made my config complete.
Recommendation for other user with the same problem:
Use the manual way for settings by editing the text-based config files.
LuCi (in my case!) didn't cover the setting complexity.
Is DSA implemented in 22.03.x ?
from ana answer I got recewntly, not. And there seem not to be plans anytime soon:
https://forum.openwrt.org/t/netgear-nighthawk-x4s-r7800-opwenwrt-versions/162511/2?u=kattivius