Regression: netplan.io does not support managing OpenVPN bridges

Status changed to 'Confirmed' because the bug affects multiple users.

For me the proposed workaround doesn't work.
On openvpn stop I get:
sep 25 11:21:51 lieta networkd-dispatcher[140803]: DEBUG:Signal: typ=dbus.String('org.freedesktop.network1.Link'), data=dbus.Dictionary({dbus.String('AdministrativeState'): dbus.String('linger', variant_level=1)}, signature=dbus.Signature('sv')), path=dbus.ObjectPath('/org/freedesktop/network1/link/_314')
sep 25 11:21:51 lieta networkd-dispatcher[140803]: DEBUG:Path '/etc/networkd-dispatcher/linger.d' does not exist; skipping
sep 25 11:21:51 lieta networkd-dispatcher[140803]: DEBUG:Path '/usr/lib/networkd-dispatcher/linger.d' does not exist; skipping
sep 25 11:21:51 lieta networkd-dispatcher[140803]: DEBUG:Ignoring notification for interface NetworkctlListState(idx=14, name='tap0', type='ether', operational='off', administrative='linger') entering state 'linger': no triggers

On openvpn start I get:
sep 25 11:22:00 lieta networkd-dispatcher[140803]: DEBUG:Signal: typ=dbus.String('org.freedesktop.network1.Link'), data=dbus.Dictionary({dbus.String('CarrierState'): dbus.String('off', variant_level=1), dbus.String('OperationalState'): dbus.String('off', variant_level=1)}, signature=dbus.Signature('sv')), path=dbus.ObjectPath('/org/freedesktop/network1/link/_315')
sep 25 11:22:00 lieta networkd-dispatcher[140803]: WARNING:Unknown index 15 seen, reloading interface list
sep 25 11:22:00 lieta networkd-dispatcher[140803]: DEBUG:Performed interface scan; state: <Dispatcher({'script_dir': '/etc/networkd-dispatcher:/usr/lib/networkd-dispatcher'})>
sep 25 11:22:00 lieta networkd-dispatcher[140803]: DEBUG:No change represented by operational state 'off' for interface 'tap0'
sep 25 11:22:00 lieta networkd-dispatcher[140803]: DEBUG:Signal: typ=dbus.String('org.freedesktop.network1.Link'), data=dbus.Dictionary({dbus.String('AdministrativeState'): dbus.String('unmanaged', variant_level=1)}, signature=dbus.Signature('sv')), path=dbus.ObjectPath('/org/freedesktop/network1/link/_315')
sep 25 11:22:00 lieta networkd-dispatcher[140803]: DEBUG:Path '/etc/networkd-dispatcher/unmanaged.d' does not exist; skipping
sep 25 11:22:00 lieta networkd-dispatcher[140803]: DEBUG:Path '/usr/lib/networkd-dispatcher/unmanaged.d' does not exist; skipping
sep 25 11:22:00 lieta networkd-dispatcher[140803]: DEBUG:Ignoring notification for interface NetworkctlListState(idx=15, name='tap0', type='ether', operational='off', administrative='unmanaged') entering state 'unmanaged': no triggers

So none of the networkd-dispatcher get executed.

Cant assign address to tap0 in Ubuntu 20.04 netplan 0.101-0ubuntu3~20.04.2

# cat /etc/systemd/network/90-tap0.netdev
[NetDev]
Name=tap0
Kind=tap

[Tap]
#Group=vhost-net
MultiQueue=yes
PacketInfo=yes

netplan config snippet:
# network: {config: disabled}
network:
    ethernets:
        tap0:
            addresses:
             - 10.255.254.1/24

    version: 2

# netplan apply
# ip addr show dev tap0
5: tap0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default qlen 1000
    link/ether 8e:9c:a6:1b:21:f1 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::8c9c:a6ff:fe1b:21f1/64 scope link
       valid_lft forever preferred_lft forever