In RouterOS there is no way to set the domain in the NTP client.

So that the router always looks at live servers - let’s create a scheduler that will constantly update the lists of servers.

On the on-event field, we write such a simple script:

:local ntpServer ""
:local primary [resolve $ntpServer]
:local secondary [resolve $ntpServer]
:local tertiary [resolve $ntpServer]

/system/ntp/client/set servers="$primary,$secondary,$tertiary"

Once a day is enough to run.