My central station is starting their push to move customers to LTE in advance of the anticipated 4G sunset. (Yes, I know it's still a ways off) I'm using a 4500EZ with serial interface to the M1 and it was looking like the only replacement option would be dialer capture, but Uplink fixed it with a new LTE 5500ATT communicator. It's a drop-in replacement for any old Uplink using the 10-pin header to serial cable. There was quite a bit of back and forth between my monitoring company and their distributor trying to get the part number right, but it is now available and on the way to me shortly.
Given how challenging/confusing it can be to DIY monitoring, I thought you all might like to know.