ntpsec-doc binary package in Ubuntu Mantic arm64

 NTP, the Network Time Protocol, is used to keep computer clocks
 accurate by synchronizing them over the Internet or a local network,
 or by following an accurate hardware receiver that interprets GPS,
 DCF-77, or similar time signals.
 .
 This package contains HTML documentation for the ntpsec packages (ntpsec,
 ntpsec-ntpdate).
 .
 This is part of NTPsec. NTPsec is a secure, hardened, and improved
 implementation derived from the original NTP project.

Source package