AllowRoot Zabbix agent

mkdir -p /etc/systemd/system/zabbix-agent.service.d
cat << 'EOF' > /etc/systemd/system/zabbix-agent.service.d/override.conf
[Service]
User=root
Group=root
EOF
systemctl daemon-reload
systemctl restart zabbix-agent

Another method with agentd:

mkdir -p /etc/systemd/system/zabbix-agent.service.d && echo -e '[Service]\nUser=root\nGroup=root' | sudo tee /etc/systemd/system/zabbix-agent.service.d/override.conf

Another method with agent2:

mkdir -p /etc/systemd/system/zabbix-agent2.service.d && echo -e '[Service]\nUser=root\nGroup=root' | sudo tee /etc/systemd/system/zabbix-agent2.service.d/override.conf

Or:

systemctl edit zabbix-agent2

Or:

systemctl edit zabbix-agent

Paste:

[Service]
User=root
Group=root

Source:
https://www.zabbix.com/documentation/current/manual/appendix/install/run_agent_as_root