Note on the Meraki - the MX67C is what you want, or CW if you do want the integrated wireless. Note that if you are going to have separate wireless APs you definitely want to skip the W model because it won't cooperate with independent WAPs.
And that's what we use in our stack. We've only bothered once but if you do want 5G you can use a dedicated 5G modem with ethernet and connect it to WAN2 on your firewall like any other failover connection.
Or if you really want integrated I'm sure Cradlepoint or Peplink have have that, integrating WWAN is sort of their bread and butter.
