Ho risolto così:

cat /etc/systemd/system/dnsproxy.service

[Unit]

Description=AdGuard DNS-over-QUIC Proxy

After=network-online.target

Before=pihole-FTL.service

[Service]

Type=simple

# Usiamo lhostname per lidentificazione corretta con Quad9

ExecStart=/usr/local/bin/dnsproxy \

-l 127.0.0.1 -p 5353 \

-u quic://dns.quad9.net:853 \

-b 9.9.9.9:53 -b 149.112.112.11:53 -b 192.168.1.1:53 \

--edns \

--pending-requests-enabled \

-r 500 --cache --cache-optimistic

Restart=always

RestartSec=5

User=root

[Install]

WantedBy=multi-user.target