ntp

System: Debian GNU/Linux (version 11.1)
CPUs: Intel(R) Core(TM) i5-3230M CPU @2.60GHz
Deps: libevent-core-2.1-7, libevent-pthreads-2.1-7,
libopts25, ntp, sntp

As root run 'apt purge systemd-timesyncd'.

If timesyncd.conf was modified the above command will delete the file.

Use the GUI frontend to apt to mark ntp and its dependencies for installation and click 'Apply'.

# sntp pool.ntp.org
sntp 4.2.8p15@1.3728-o Wed Sep 23 11:46:38 UTC 2020 (1)
2021-11-06 17:04:11.040104 (+0600) +0.002633 +/- 0.029465 pool.ntp.org 62.201.225.9 s2 no-leap
# /sbin/hwclock --systohc --localtime
# ls -l /etc/adjtime
-rw-r--r-- 1 root root 46 Nov 6 17:04 /etc/adjtime
# cat /etc/adjtime
0.000000 1636236347 0.000000
1636236347
LOCAL
#

If one prefers setting their hardware clock to UTC change the command to 'hwclock --systohc --utc'.