I've an M5Stack Fire and the LTE/4G module, and have spent dozens of hours trying in vain to get an HTTPS site to load.
Here are my findings:
ESP-IDF v4.4 - got as far as establishing an LTE connection, but random semaphore exceptions were causing crashes.
Arduino - got HTTP Get working but HTTPS handshake failed, error code 715. guessing because of cert not available, and no easy way of uploading them to the GSM7600 module. Couldn't get TinyGsm modem working.
UIFlow - was able to put Fire in Internet mode, set APN and add the required cert, it all looked great in terms of LTE connection - but when I then tried to run my app from the Apps widget on the device, it reboots before running it - losing the LTE connection it's just spent 2 minutes establishing!
I regard working with M5Stack products as a proper hacker challenge - working to stitch together what's needed from patchy documentation and few examples...
...but this one genuinely has got me beat at this point.
If anyone could point me in the right direction of a working example of HTTPS retrieval using LTE/4G rather than wifi, using any of the tools above, I'd be eternally grateful!