systemd-resolved now listens on the local IP address 127.0.0.53:53 for DNS requests. This improves compatibility with local programs that do not use the libc NSS or systemd-resolved's bus APIs for name resolution. This minimal DNS service is only available to local programs and does not implement the full DNS protocol, but enough to cover local DNS clients.
A new, static resolv.conf file, listing just this DNS server is now shipped in /usr/lib/systemd/resolv.conf. It is now recommended to make /etc/resolv.conf a symlink to this file in order to route all DNS lookups to systemd-resolved, regardless if done via NSS, the bus API or raw DNS packets.