I do not know why this should not work with the L5 modem. Many years ago I owned cellphones, like the Siemens S10, or some Bosch 908 device. They have had V.24. interface, you connected your computer/laptop to it, used kermit to dial ATD1234567 and when it got CONNECT 9600 (9600 baud) you could either talk to the other site offering login: or both ends launched PPP daemons. This was over GSM as carrier, but the called site was a POTS number, i.e. analog. GSM hanled this transparently to your end to V.24. Why should this not work over LTE?
Just run a test, install kermit and dial:
mmcli -h
mmcli -L (gives the modem number)
mmcli --modem=3
mmcli --modem=any (as we have only one modem)
how to make an shortcut icon for a small terminal app, see:
https://forums.puri.sm/t/shortcut-to-modem-info/16886
cat ~/.kermrc
set escap 21
set line /dev/ttyUSB3
set carrier-watch off
$ sudo kermit ~purism/.kermrc
C-Kermit 9.0.305 OPEN SOURCE: Alpha.02, 19 Sep 2020, for Linux+SSL+KRB5 (64-bit)
Copyright (C) 1985, 2020,
Escape character: Ctrl-U (ASCII 21, NAK): enabled
Type the escape character followed by C to get back,
or followed by ? to see other options.
(/home/purism/) C-Kermit> connect
atd 1234567890
...
and see what will happen… I could do the test as well, but don’t have any number to dial which is a analog modem.
PS: The Bosch 908 was in March 1999 as I could check in my mails. The Bosch company in Germany lent me the device for such tests.