Wanted to update this with a simpler solution that builds on the reply from @buckbaggen above.
- chrony seems installed by default now on Synology DSM 7.x +
- I only needed to create /etc/chrony.conf.user with the following two lines only, included from the earlier solution:
makestep 1 3
rtcsyncde here
Then I did a quick restart of the service, as above:
systemctl restart chronyd
This was on a DS920+ and DS416play. The errors have went away in netdata within seconds after restarting chrony. Will see if it sticks.
netdata-parent2 netdata[13943]: ALERT 'system_clock_sync_state' of instance 'system.clock_sync_state' on node 'NODENAME', transitioned from WARNING to CLEAR