So, named service is stopped:
sudo update-rc.d -f named remove
sudo: unable to resolve host server1.localdomain: Temporary failure in name resolution
zalmoxis@server1:~$ sudo systemctl status named.service
sudo: unable to resolve host server1.localdomain: Temporary failure in name resolution
● named.service - BIND Domain Name Server
Loaded: loaded (/lib/systemd/system/named.service; enabled; vendor preset: enabled)
Active: inactive (dead) since Thu 2021-07-22 11:55:00 CEST; 35min ago
Docs: man:named(8)
Main PID: 591 (code=exited, status=0/SUCCESS)
Jul 22 11:55:00 server1.localdomain named[591]: received control channel command 'stop'
Jul 22 11:55:00 server1.localdomain named[591]: no longer listening on 127.0.0.1#53
Jul 22 11:55:00 server1.localdomain named[591]: no longer listening on ::1#53
Jul 22 11:55:00 server1.localdomain named[591]: no longer listening on fe80::207:cbff:fe0b:7577%2#53
Jul 22 11:55:00 server1.localdomain named[591]: shutting down: flushing changes
Jul 22 11:55:00 server1.localdomain named[591]: stopping command channel on 127.0.0.1#953
Jul 22 11:55:00 server1.localdomain named[591]: stopping command channel on ::1#953
Jul 22 11:55:00 server1.localdomain named[591]: exiting
Jul 22 11:55:00 server1.localdomain systemd[1]: named.service: Succeeded.
Jul 22 11:55:00 server1.localdomain systemd[1]: Stopped BIND Domain Name Server.
Still:
sudo update-rc.d -f named remove
sudo: unable to resolve host server1.localdomain: Temporary failure in name resolution