Thank you for reporting.
This could be a regression due to a fix for this issue: Unable to disable legacy LuCI UI after system upgrade · Issue #760 · NethServer/nethsecurity · GitHub
I can’t reproduce your problem on a clean machine.
Could you please paste the output of the following commands?
Commands:
uci show ns-ui
find /etc/nginx/
/usr/sbin/nginx -T -c /etc/nginx/uci.conf
cat /etc/nginx/uci.conf