The service is failing to start.

root@DietPi:# sudo service unbound restart
Job for unbound.service failed because the control process exited with error code.
See "systemctl status unbound.service" and "journalctl -xe" for details.
root@DietPi:# systemctl status unbound.service
● unbound.service - Unbound DNS server
Loaded: loaded (/lib/systemd/system/unbound.service; enabled; vendor preset: enabled)
Drop-In: /etc/systemd/system/unbound.service.d
└─dietpi.conf
Active: failed (Result: exit-code) since Sat 2023-08-12 19:14:21 BST; 17s ago
Docs: man:unbound(8)
Process: 6870 ExecStartPre=/usr/lib/unbound/package-helper chroot_setup (code=exited, status=0/SUCCESS)
Process: 6873 ExecStartPre=/usr/lib/unbound/package-helper root_trust_anchor_update (code=exited, status=0/SUCCESS)
Process: 6876 ExecStart=/usr/sbin/unbound -d -p $DAEMON_OPTS (code=exited, status=1/FAILURE)
Process: 6877 ExecStopPost=/usr/lib/unbound/package-helper chroot_teardown (code=exited, status=0/SUCCESS)
Main PID: 6876 (code=exited, status=1/FAILURE)
CPU: 170ms

Aug 12 19:14:21 DietPi systemd[1]: unbound.service: Scheduled restart job, restart counter is at 5.
Aug 12 19:14:21 DietPi systemd[1]: Stopped Unbound DNS server.
Aug 12 19:14:21 DietPi systemd[1]: unbound.service: Start request repeated too quickly.
Aug 12 19:14:21 DietPi systemd[1]: unbound.service: Failed with result 'exit-code'.
Aug 12 19:14:21 DietPi systemd[1]: Failed to start Unbound DNS server.

To reproduce
Steps to reproduce the behavior:

1. Delete any old installation Unbound, as it was non-functioning
2. Reinstall Unbound

Expected behavior
A clear and concise description of what you expected to happen.

1. sudo apt install unbound
2. unbound.works=true

System:

• Unbound version: 1.13.1
• OS: DietPi v8.20.1
• unbound -V output:
  root@DietPi:~# unbound -V
  Version 1.13.1

Configure line: --build=aarch64-linux-gnu --prefix=/usr --includedir=${prefix}/include --mandir=${prefix}/share/man --infodir=${prefix}/share/info --sysconfdir=/etc --localstatedir=/var --disable-option-checking --disable-silent-rules --libdir=${prefix}/lib/aarch64-linux-gnu --libexecdir=${prefix}/lib/aarch64-linux-gnu --disable-maintainer-mode --disable-dependency-tracking --disable-rpath --with-pidfile=/run/unbound.pid --with-rootkey-file=/var/lib/unbound/root.key --with-libevent --with-pythonmodule --enable-subnet --enable-dnstap --enable-systemd --with-chroot-dir= --with-dnstap-socket-path=/run/dnstap.sock --libdir=/usr/lib --disable-flto
Linked libs: libevent 2.1.12-stable (it uses epoll), OpenSSL 1.1.1n 15 Mar 2022
Linked modules: dns64 python subnetcache respip validator iterator

BSD licensed, see LICENSE in source package for details.
Report bugs to unbound-bugs@nlnetlabs.nl or https://github.com/NLnetLabs/unbound/issues

Additional information
I was following the Unbound guide from pi-hole.net, but had to stop after the first step. I have no idea how to troubleshoot anything related to Linux.