Active-backup bonding in netplan using cellural modem

I try to set up active-backup bonding in netplan with a modem (ppp0) as a backup. Ppp0 interface works correctly on its own and was created using network manager in line with the guide on official ubuntu website:

sudo nmcli c add type gsm ifname '*' con-name "GSM" apn "internet'

As far as I understand, to create a bond in netplan, I have two options:

1. Add ppp0 connection without changing of NM configuration
2. Manage ppp0 connection through netplan

However, in both options as soon as I do "netplan apply" ppp0 connection is not longer working which is visible in ifconfig. Without netplan "ping" works and the connection has IP address:

ppp0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST>  mtu 1500
    inet 10.72.119.39  netmask 255.255.255.255  destination 0.0.0.0
    ppp  txqueuelen 3  (Point-to-Point Protocol)
    RX packets 6  bytes 84 (84.0 B)
    RX errors 0  dropped 0  overruns 0  frame 0
    TX packets 8  bytes 143 (143.0 B)
    TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

with netplan config applied, ping doesn't work and ifconfig doesn't show IP

ppp0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST>  mtu 1500
    ppp  txqueuelen 3  (Point-to-Point Protocol)
    RX packets 32  bytes 2268 (2.2 KB)
    RX errors 0  dropped 0  overruns 0  frame 0
    TX packets 251  bytes 20555 (20.5 KB)
    TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

Netplan config which I am using:

network:
  version: 2
  renderer: NetworkManager
  ethernets:
    enp2s0:
      dhcp4: true
    enp4s0:
      dhcp4: true
  modems:
    ppp0: {}
  bonds:
    bond0:
      interfaces:
        - enp2s0
        - ppp0
      parameters:
        mode: active-backup
        primary: enp2s0

The second option gives the same results regardless of netplan config. I'm stuck - what I am doing wrong?