https://documentation.meraki.com/MX/Cellular/3G//4G_Cellular_Failover_with_USB_Modems lists all compatible USB modems. 5G is not supported from my point of view.
Some cards are only available from some carriers. Some cards are only approved for use in certain countries. Some carriers block non approved cards.
The easy option is to use the MG21 (although note there were two versions depending on where you are in the world).
The gateway connects via RJ45 whereas we are looking for a 5G option that connected directly to the USB on the Device. Not to worry. Thanks all.