Comment 9 for bug 1967084

I managed to capture a debug log from netplan when run via the ddbus comments in #8. It was a bit tricky (bind mounted utils.py and set debug = True there) because netplan is coming from a RO location and no way to use the environment to enable debugging. Unfortunately the log gives me not many hints:
"""
qemu:ubuntu-core-20-64 .../tests/core/netplan-cfg# dbus-send --type=method_call --system --print-reply --dest=io.netplan.Netplan /io/netplan/Netplan/config/PCJPK1 io.netplan.Netplan.Config.Try uint32:300
DEBUG:all-en not found in {}
DEBUG:all-eth not found in {'all-en': {'match': {'name': 'en*'}, 'dhcp4': True}}
DEBUG:br54 not found in {}
DEBUG:Merged config:
network:
  bridges:
    br54:
      dhcp4: true
  ethernets:
    all-en:
      dhcp4: true
      match:
        name: en*
    all-eth:
      dhcp4: true
      match:
        name: eth*
  version: 2

DEBUG:New interfaces: set()
DEBUG:netplan generated networkd configuration changed, reloading networkd
DEBUG:all-en not found in {}
DEBUG:all-eth not found in {'all-en': {'match': {'name': 'en*'}, 'dhcp4': True}}
DEBUG:br54 not found in {}
DEBUG:Merged config:
network:
  bridges:
    br54:
      dhcp4: true
  ethernets:
    all-en:
      dhcp4: true
      match:
        name: en*
    all-eth:
      dhcp4: true
      match:
        name: eth*
  version: 2

DEBUG:no netplan generated NM configuration exists
DEBUG:all-en not found in {}
DEBUG:all-eth not found in {'all-en': {'match': {'name': 'en*'}, 'dhcp4': True}}
DEBUG:br54 not found in {}
DEBUG:Merged config:
network:
  bridges:
    br54:
      dhcp4: true
  ethernets:
    all-en:
      dhcp4: true
      match:
        name: en*
    all-eth:
      dhcp4: true
      match:
        name: eth*
  version: 2

DEBUG:Link changes: {}
DEBUG:all-en not found in {}
DEBUG:all-eth not found in {'all-en': {'match': {'name': 'en*'}, 'dhcp4': True}}
DEBUG:Merged config:
network:
  ethernets:
    all-en:
      dhcp4: true
      match:
        name: en*
    all-eth:
      dhcp4: true
      match:
        name: eth*
  version: 2

DEBUG:netplan triggering .link rules for lo
DEBUG:netplan triggering .link rules for ens3
DEBUG:netplan triggering .link rules for br54
DEBUG:all-en not found in {}
DEBUG:all-eth not found in {'all-en': {'match': {'name': 'en*'}, 'dhcp4': True}}
DEBUG:br54 not found in {}
DEBUG:Merged config:
network:
  bridges:
    br54:
      dhcp4: true
  ethernets:
    all-en:
      dhcp4: true
      match:
        name: en*
    all-eth:
      dhcp4: true
      match:
        name: eth*
  version: 2

method return time=1649661702.221874 sender=:1.40 -> destination=:1.45 serial=12 reply_serial=2
   boolean false
"""
but maybe it's more useful for you?