Debian 13 (Trixie) ships with NetworkManager which the author struggles to utilise in the command line. The classical network configuration through /etc/network/interfaces still works.
NetworkManager can be configured through the file at /etc/NetworkManager/system-connections. It appear in the author’s current implementation, the system must be rebooted for changes to take effect; reloading the daemons doesn’t work…
resolv.conf contains the DNS nameservers. It is managed by NetworkManager.
Further reading
- The man pages