Raspberry Pi GSM Module - Mobile Internet (LTE, 3G, UMTS)
Amazon.com: 4G / 3G / GNSS HAT Module for Raspberry Pi Zero/Zero W/Zero WH/2B/3B/3B+/4B/Jetson Nano, Based on SIM7600A-H , 4G Communication and GNSS Positioning Module Support LTE CAT4 up to 150Mbps :
Raspberry Pi and 3G connectivity from TDC Denmark
Amazon.com: GeeekPi RPi 4G / 3G Hat for Raspberry Pi Zero/Zero W/Zero WH/2B/3B/3B+/4B,Jetson Nano,Supports SMS, MMS, Mail, TCP, UDP, DTMF, HTTP, FTP : Electronics
Raspberry Pi - Huawei HiLink E3256 3G mobile broadband USB dongle to RJ45 ethernet router
Raspberry Pi Skywire Adapter | Airgain
3G Internet on Raspberry Pi – Success! – Terence Eden's Blog
Raspberry Pi 3G/4G-LTE Base HAT
Giving the Raspberry Pi a Serial Modem Using the HUAWEI E3531 USB Dongle (+ Send SMS) : 6 Steps - Instructables
USB modem power issues
Raspberry Pi SIM7600CE-CNSE 4G DONGLE User Guide
Tutorial - Using Cellular Modems with the Raspberry Pi 4B - SwitchDoc Labs Blog
SixFab Launches Raspberry Pi 3G-4G/LTE Base Shield V2 for $31.20 - CNX Software
Modem LTE/3g /2g with raspberry pi 3/4 A+/B+... - Hackster.io