Great thread!!! I've been using T-Mobile home internet since it first came out with the little white LTE gateway. My setup has really morphed over time. I abandoned the stock gateways because they lack features and control.
The white router is the Glinet Spitz GL-X3000. You can adjust TTL, IMEI etc. It also does 2X 5G bands carrier aggregation, either NSA or SA. You can tower lock as well as band lock. The router has way too many features to list here so I'll leave a link.
A WiFi 6 Dual-SIM 4G/5G Cellular Router that supports 5G NR Dual-SIM Failover & Multi-WAN, pre-installed with OpenWrt 21.02, OpenVPN and WireGuard.
www.gl-inet.com
I have the Spitz connected to a Waveform 4X4 mimo antenna. I have the wifi disabled on the Spitz because I use a TP Link Omada setup for wifi.