under those optional interfaces, that should prevent netplan for asking to dhcp on those interfaces.
The docs indicate that dhcp4/dhcp6 are off by default, so there may still be a bug here
in that the composed devices (bridge/bonds) dhcp values are getting set on members.
I believe if you put:
dhcp4: no
dhcp6: no
under those optional interfaces, that should prevent netplan for asking to dhcp on those interfaces.
The docs indicate that dhcp4/dhcp6 are off by default, so there may still be a bug here
in that the composed devices (bridge/bonds) dhcp values are getting set on members.