no problem is found for dial up in ubuntu 12 using usb /dev/ttyACM1 port with FW 4.6.8.0:
Cowner@ubuntu:~$ sudo wvdial
→ WvDial: Internet dialer version 1.61
→ Initializing modem.
→ Sending: AT
AT
OK
→ Modem initialized.
→ Sending: ATDT991#
→ Waiting for carrier.
A
CONNECT
TDT99**1#
→ Carrier detected. Waiting for prompt.
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→ PPP negotiation detected.
→ Starting pppd at Wed Sep 1 16:28:58 2021
→ Pid of pppd: 3507
→ Using interface ppp0
→ local IP address 10.12.2.136
→ remote IP address 10.0.0.1
owner@ubuntu:~$ sudo cat /etc/wvdial.conf
[sudo] password for owner:
[Dialer Defaults]
Phone = 99**1#
Username = 1
Password = 1
New PPPD = yes
Baud = 115200
Modem = /dev/ttyACM1
PPPD Path = /usr/sbin/pppd
Modem Type = Analog Modem
Auto Reconnect = on
Carrier Check = no
Init1 = AT
owner@ubuntu:~$ ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_req=1 ttl=116 time=1864 ms
64 bytes from 8.8.8.8: icmp_req=2 ttl=116 time=966 ms
64 bytes from 8.8.8.8: icmp_req=3 ttl=116 time=333 ms
^C
— 8.8.8.8 ping statistics —
3 packets transmitted, 3 received, 0% packet loss, time 2010ms
rtt min/avg/max/mdev = 333.693/1054.671/1864.228/627.969 ms, pipe 2
owner@ubuntu:~$