DNS

Disable systemd-resolved if you want to use plain resolv.conf.
Either use router's DNS: Restart machine to have and updates resolv.conf file.
Use dedicated DNS, e.g. see https://www.kuketz-blog.de/empfehlungsecke/#dns or your own.
Edit resolv.conf by making it immutable afterwards: sudo chattr -i /etc/resolv.conf; sudo nano /etc/resolv.conf; sudo chattr +i /etc/resolv.conf
```
options timeout:1
options single-request
# IPv4
nameserver ...
# IPv6
nameserver .............
```