How to add 5G/LTE to a ESP32C3 custom board

[mzincali]

I've got a working circuit using ESP32C3. I now need to provide network access for those situations where WiFi isn't available. What's the best place to start? I am not opposed to replace the ESP32C3, but would rather not. I do realize that LTE/5G will have monthly access fees and more complexity. I see:

• https://www.adafruit.com/product/2542 - Overkill? I don't need voice at all. SMS is kinda cool, so I could take it or leave it.
  https://www.adafruit.com/product/2636 - same. Overkill?
  https://www.adafruit.com/product/4753

Also, I haven't yet looked at LoRa or other networking, so if that is preferable, I'd love some pointers. I see https://www.adafruit.com/product/3998, but I'm curious if there is a way to just add LoRa to an existing custom design (of course, I'm first going to have to prototype it using whatever breakout boards etc available).

Thank you!

[MicroController]

What kind of "network access" do you want?
The modules you found/linked to are "2G" modules (GSM+GPRS), not 5G and not LTE. If you have 2G coverage you can access the internet via GPRS, at about 50kbit/s IIRC (yes, that is KILO bits per second), which may or may not be sufficient for your application.

Most, if not all, of the mobile network chips and modules support voice calls out of the box; if you don't need that, just don't use the feature. Usually, the modules are controlled via a serial (UART) interface so you can connect them to any circuit you design where you have a serial port available.

LoRa is a completely different technology to cellular phone networks. Basically, LoRa only defines a protocol to send and receive data over radio frequency, directly from one LoRa device to another one. There are projects, many community-driven, to create cellular network like infrastructure to forward messages between LoRa devices or even to/from the internet; see if that'd be of use to your application. Plus, LoRa is designed for long range and very low power consumption and, as a result, provides very limited data rates as well, absolutely nowhere near those of 5G or LTE.
As for cell phone networks, there are dedicated chips and modules for LoRa communication which you'd connect to your controller via e.g. SPI.

[mzincali]

Thank you. My research has identified two good (or great) options: LTE-M and NB-IoT. They both seem to have some penetration and network coverage, and they're both low power, and not too complex to add to a board (compared to other cellular). My bandwidth needs are relatively simple:periodically I want to send 1K of data at most, and may receive about 100 bytes of data back.

The only issue is that if I need to do a firmware update, these network options are too slow and too expensive. I'd like to have WIFi still available for that situation, but that might be too much on one small board.