The ntpd distributions from ntp.org and ntpsec.org include a program called “ntptime”.
$ ntptime
ntp_gettime() returns code 0 (OK)
time e2bace6b.a63dd510 Thu, Jul 16 2020 8:02:35.649, (.649381825),
maximum error 112136 us, estimated error 55 us, TAI offset 0
ntp_adjtime() returns code 0 (OK)
modes 0x0 (),
offset 41.186 us, frequency -6.451 ppm, interval 1 s,
maximum error 112136 us, estimated error 55 us,
status 0x2001 (PLL,NANO),
time constant 6, precision 0.001 us, tolerance 500 ppm,
Try running ntptime once/minute. Does the offset and frequency change?