Just made a thing to let LTE module start on boot.
Done in systemd unit files.
This can handle module power on, Modem Manager startup queueing and restart Modem Manager with the LTE module.
The only downside currently is delayed shutdown for about 30s, for LTE module safe shutdown.
https://gist.github.com/SuperMarioSF/baea9fc13fc320e5a002c58cf107bd10