Ardexa Linux uses systemctl-timesyncd for clock synchronisation. This will be autmatically done.
For troubleshooting, or to configure one or more local, custom NTP servers, first scan the local network for port 123/udp
# scan the local network for open NTP ports, your IP subnet will
# most likely be different. Routers are most likely to have the port
# open and active
nmap -sU -p 123 192.168.1.0/24
# check the port is actually responding to requests