pfSense

System|Advanced|Networking:
When you switch from ISC DHCP to Kea DHCP, the configuration is migrated. Unfortunately, the Kea DHCP server is not started, an error message can be found under Status|System Logs|DHCP:

Oct 16 15:16:44     kea-dhcp4     16667     ERROR [kea-dhcp4.dhcp4.0x4909f612000] DHCP4_INIT_FAIL failed to initialize Kea server: configuration error using file '/usr/local/etc/kea/kea-dhcp4.conf': option data does not match option definition (space: dhcp4, code: 42): Failed to convert string to address 'ntp_net.sm.art': Invalid argument (/usr/local/etc/kea/kea-dhcp4.conf:88:33)

Under Services|DHCP Server|NET no IP addresses but hostnames are entered as NTP servers. The Kea DHCP server obviously cannot resolve hostnames and requires IP addresses at this point.

Improvement : The Kea DHCP server should be able to resolve hostnames.
Workaround : Use IP addresses until then.
Note : Simply switching back to the ISC DHCP server is problematic if DHCP options were used in the ISC DHCP. These are deleted after switching back. Workaround: Before switching to Kea DHCP, back up the complete pfsense configuration and restore it if necessary.