EM7455 in D-Link locked to Verizon

Hello folks! I’m new here, but saw a few posts about something I’m having trouble with and thought maybe I could get some help.
I’ve bought a gently used D-Link router that is locked to Verizon (I didn’t realize this when buying it). When I put the IMEI into one of those unlock websites, it was recognized as Sierra Wireless EM 7455. I saw one post on here from a couple years ago saying that these units were turned into wireless devices instead of being used in laptops.
I don’t really know yet how to install firmware on my router, but I’m guessing there’s firmware I can install to replace the Verizon-only firmware that’s on it now. Do any of you know a safe place I can get such a file? And can anyone refer me to instructions on installing it onto my router?
Thanks very much in advance!

here is the firmware page of EM7455: