pfSense

Please consider chronyd's advantages and disadvantages vs ntpd - see https://chrony.tuxfamily.org/comparison.html

In my opinion, chrony is better for the job, for security, management and performance reasons. Red Hat, for example, has it in its list of supported packages and it's enabled by default on RHEL8 (https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/system_administrators_guide/ch-configuring_ntp_using_the_chrony_suite)

There's a great guide for migration + script on https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/configuring_basic_system_settings/using-chrony-to-configure-ntp