NuttShell (NSH) NuttX-9.1.0
nsh> pppd &
pppd [3:100]
nsh> chat: ATZ

~�}#�!}%}!} }$=�~~�}#�!}%}"} }$Y(~+++
Call Ready
ATE1
OK
chat: OK
ATZ
OK
chat: cmd 1, arg ON

chat: cmd 4, arg 30

chat: ATE1

chat: OK AT+QACCM=0,0

ATE1
OK
chat: OK AT+CGDCONT=1,"IP","tim.br"

AT+QACCM=0,0
OK
chat: OK ATD99**1#

AT+CGDCONT=1,"IP","tim.br"
OK
chat: CONNECT
ATD99**1#
CONNECT

nsh> ifconfig
ppp0 Link encap:TUN at UP
inet addr:100.97.122.249 DRaddr:192.168.254.254 Mask:0.0.0.0

nsh> ping 8.8.8.8
PING 8.8.8.8 56 bytes of data
56 bytes from 8.8.8.8: icmp_seq=0 time=800 ms
56 bytes from 8.8.8.8: icmp_seq=1 time=690 ms
56 bytes from 8.8.8.8: icmp_seq=2 time=720 ms
56 bytes from 8.8.8.8: icmp_seq=3 time=610 ms
56 bytes from 8.8.8.8: icmp_seq=4 time=640 ms
56 bytes from 8.8.8.8: icmp_seq=5 time=670 ms
56 bytes from 8.8.8.8: icmp_seq=6 time=560 ms
56 bytes from 8.8.8.8: icmp_seq=7 time=590 ms
56 bytes from 8.8.8.8: icmp_seq=8 time=620 ms
56 bytes from 8.8.8.8: icmp_seq=9 time=650 ms
10 packets transmitted, 10 received, 0% packet loss, time 10100 ms
nsh>

This is my defconfig:

# CONFIG_ARCH_FPU is not set
# CONFIG_NSH_ARGCAT is not set
# CONFIG_NSH_CMDPARMS is not set
CONFIG_ARCH="arm"
CONFIG_ARCH_BOARD="xxxxx-zz0035"
CONFIG_ARCH_BOARD_XXXXX_ZZ0035=y
CONFIG_ARCH_CHIP="stm32l4"
CONFIG_ARCH_CHIP_STM32L496RE=y
CONFIG_ARCH_CHIP_STM32L4=y
CONFIG_ARCH_INTERRUPTSTACK=2048
CONFIG_ARCH_STACKDUMP=y
CONFIG_ARMV7M_STACKCHECK=y
CONFIG_BOARD_LOOPSPERMSEC=8499
CONFIG_BUILTIN=y
CONFIG_CLOCK_MONOTONIC=y
CONFIG_DEBUG_SYMBOLS=y
CONFIG_XXXXX_ZZ0035_QUECTEL_M95=y
CONFIG_EXAMPLES_ABNTCODI=y
CONFIG_EXAMPLES_ALARM=y
CONFIG_EXAMPLES_PPPD=y
CONFIG_EXAMPLES_RANDOM=y
CONFIG_FS_PROCFS=y
CONFIG_FS_PROCFS_REGISTER=y
CONFIG_HAVE_CXX=y
CONFIG_HAVE_CXXINITIALIZE=y
CONFIG_I2C=y
CONFIG_I2CTOOL_MAXBUS=4
CONFIG_I2CTOOL_MINBUS=1
CONFIG_I2C_RESET=y
CONFIG_INTELHEX_BINARY=y
CONFIG_MAX_TASKS=16
CONFIG_MAX_WDOGPARMS=2
CONFIG_MM_REGIONS=2
CONFIG_NET=y
CONFIG_NETDEVICES=y
CONFIG_NETDEV_LATEINIT=y
CONFIG_NETUTILS_PPPD_PAP=y
CONFIG_NET_ARP_SEND=y
CONFIG_NET_ICMP=y
CONFIG_NET_ICMP_SOCKET=y
CONFIG_NET_ROUTE=y
CONFIG_NET_SOCKOPTS=y
CONFIG_NET_TCP=y
CONFIG_NET_UDP=y
CONFIG_NFILE_DESCRIPTORS=8
CONFIG_NFILE_STREAMS=8
CONFIG_NSH_ARCHINIT=y
CONFIG_NSH_BUILTIN_APPS=y
CONFIG_NSH_FILEIOSIZE=512
CONFIG_NSH_LINELEN=64
CONFIG_NSH_READLINE=y
CONFIG_PREALLOC_MQ_MSGS=4
CONFIG_PREALLOC_TIMERS=4
CONFIG_PREALLOC_WDOGS=8
CONFIG_RAM_SIZE=98304
CONFIG_RAM_START=0x20000000
CONFIG_RAW_BINARY=y
CONFIG_READLINE_CMD_HISTORY=y
CONFIG_READLINE_TABCOMPLETION=y
CONFIG_RR_INTERVAL=200
CONFIG_RTC_ALARM=y
CONFIG_RTC_DATETIME=y
CONFIG_RTC_DRIVER=y
CONFIG_RTC_IOCTL=y
CONFIG_RTC_NALARMS=2
CONFIG_SCHED_LPWORK=y
CONFIG_SCHED_WAITPID=y
CONFIG_SDCLONE_DISABLE=y
CONFIG_SERIAL_TERMIOS=y
CONFIG_SPI=y
CONFIG_STACK_COLORATION=y
CONFIG_STM32L4_DISABLE_IDLE_SLEEP_DURING_DEBUG=y
CONFIG_STM32L4_DMA1=y
CONFIG_STM32L4_DMA2=y
CONFIG_STM32L4_PWR=y
CONFIG_STM32L4_RNG=y
CONFIG_STM32L4_RTC=y
CONFIG_STM32L4_SAI1PLL=y
CONFIG_STM32L4_SRAM2_HEAP=y
CONFIG_STM32L4_UART4=y
CONFIG_STM32L4_USART2=y
CONFIG_STM32L4_USART3=y
CONFIG_SYSTEM_I2CTOOL=y
CONFIG_SYSTEM_NSH=y
CONFIG_SYSTEM_PING=y
CONFIG_SYSTEM_STACKMONITOR=y
CONFIG_SYSTEM_TEE=y
CONFIG_TASK_NAME_SIZE=0
CONFIG_TESTING_OSTEST=y
CONFIG_UART4_SERIAL_CONSOLE=y
CONFIG_USART2_BAUD=110
CONFIG_USART3_IFLOWCONTROL=y
CONFIG_USART3_OFLOWCONTROL=y
CONFIG_USER_ENTRYPOINT="nsh_main"
CONFIG_WDOG_INTRESERVE=1

This is the modification I did in my apps/examples/pppd/pppd_main.c