See Help GL-X3000 Spitz AX Using Visible SIM - #13 by pwyngaard
I changed the IMEI per this thread to an ulocked iPhone 13 (last one with a physical SIM) and TTL/HL to 88. Note the post that states how to lock in the IMEI change after setting the IMEI so it survives reboot. In my case (rural), I band-locked to LTE-only because it was 2x better throughput than the 5G. I am on the $25/month plan. I am consistently seeing ~60Mbps DL and ~5Mbps UL (both of which are very good for where I live).