What is the method used to have a server message appear in local every 10 minutes, for example sending out a link to discord or livemap? I have used MOTD, but that only appears when you load, how about timed messages?

You can use the Livemap -> RCON Console -> Task Scheduler

I use basilmod > MotD - it allows you to create custom messages for which you can set the timer, channel (system and local only, global not working) as well as color and font.