@danilo-burdese hi plz use below method for making a PPP internet purpose.
step1: opkg update
opkg install chat comgt
Step2: vi /etc/config/network
config interface 'hologram'
option defaultroute 1
option device /dev/ttyS1
option apn jionet //jionet place use your network apn
option service umts
option proto 3g
option 'pppd_options' 'noipdefault'
Step3: vi /etc/config/firewall
this you have to copy config forwarding above line.
config zone
option name 'cellular'
option output 'ACCEPT'
option forward 'REJECT'
option masq '1'
option mtu_fix '1'
option network 'hologram'
option input 'ACCEPT'
Step4: /etc/init.d/firewall restart
Step5: /etc/init.d/network restart
that's it thank you.