moving from NetworkManager to systemd-resolved

Can someone explain how systemd-resolved works? After reinstall to fedora 33 from fedora 30, I cannot use obsolete SNX VPN. The root cause is that DNS records are not updated. Before when I started snx vpn, new dns records appeared in /etc/resolv.conf, which content looked like:

cat resolv.conf# Generated by NetworkManagernameserver A.B.C.Dnameserver 8.8.8.8search <some urls>

now this file contains this:

# This file is managed by man:systemd-resolved(8). Do not edit.## This is a dynamic resolv.conf file for connecting local clients to the# etc.

and its content does not react to vpn being started.

It seems to be, that some bridging from NetworkManager to systemd-resolved is not working. Arch wiki mentions need to install systemd-resolvconf for legacy programs, but this is not available for fedora.

Questions:

1. how to make it work automatically? When I start snx vpn, before there was (probably, no idea what happened actually) some communication with NetworkManager resulting in regenerated resolv.conf. How to fix fedora 33, so that snx still updates list of nameservers and search patterns.

2. if that is not possible for whichever reason, how to manually add dns records now, ideally using some script not to have to click it on some gui.