How To Transfer Files from Old iMac to New

In fact, it is not generally recommended that data be moved wirelessly when migrating from an old Mac to a new. Lots of failures that way.

By far the easiest and fastest way to migrate you stuff will be to use a Time Machine backup drive from the old Mac. Make a final backup to the drive, and then when you first boot your new Mac, connect the TM backup drive to it and run the Setup Assistant. Eventually you will be asked if you'd like to transfer or migrate data from another computer and you will select the TM drive as the source. It doesn't get much easier.

Transfer to a new Mac with Migration Assistant - Apple Support

When done with the migration, continue to use the TM backup drive with the new Mac to back up your stuff. None if your data is ever really safe unless you have a backup strategy. Apple includes the software in the macOS, all you have to do is supply an external drive.

Back up your Mac with Time Machine - Apple Support

Migrating over your local network is slow and unreliable.

Migrating over a direct Ethernet connection is better, if both iMac’s have Ethernet ports.

The fastest and most reliable way to migrate that much data is to use an external drive. Make a Time Machine backup or a Clone backup of the 2019 iMac. Then plug that external drive into the new Mac and migrate during the initial setup.

You have a couple options for making a direct connection between two Macs: Ethernet cable or Thunderbolt cable.

If your new iMac has an Ethernet port - located on the AC power adapter brick - then you can connect the two with a standard Ethernet cable. A crossover cable is not required per Apple guidance. I suggest that you might also connect the Macs to the same router with Ethernet cables to make a connection.

Use Ethernet to connect two Mac computers - Apple Support

Because both of your iMacs have Thunderbolt ports you can also use a Thunderbolt 3 or Thunderbolt 4 cable to connect them. Use IP over Thunderbolt to connect Mac computers - Apple Support

I'm unable to locate any Apple guidance regarding making a direct connection between two Macs specific to the purpose of using Migration Assistant. All I find in that regard is the statement that the two Macs should be connected to the same wireless network. This is noted in the link in my first post.

IMHO, the best way to migrate your files remains using a Time Machine backup drive. It's dead simple. If you don't have a TM backup, you should. This might be a great time and excuse to create one.

You do not connect the two Macs. You connect your TM backup drive from your old Mac to the new Mac and migrate that way.

Yes I read it, however it is much smarter to use the Time Machine or external clone External Hard Disk method. Why, because it's dead reliable, fast and you can always use the External Hard Disk for your new Mac's backup!

Don't use this method and your migration may or may not work. It's really up to you whether you want to gamble or know that your migration will work.

Migration is extremely simple if you follow the steps in Setup Assistant and Migration Assistant!!!!