Did you read the comments in the guide thread?
There were a few different approaches people used. It’s been forever since I did this, so my memory is a bit hazy, but I can say that my current netplan is:
# This is the network config written by 'subiquity'
network:
ethernets:
eno1:
dhcp4: true
eno2:
dhcp4: true
version: 2
bridges:
br0:
dhcp4: yes
interfaces:
- eno1
parameters:
stp: true
vlans:
vlan40:
accept-ra: no
id: 40
link: eno2
that was set up as described. The Ubuntu system is running on 10.0.30.21, and I have a pi-hole running a 10.0.30.43, which works fine for me.
Have you tried simplifying? Removing all the config options from the ethernets? I only have the dhcp4: true, letting the router take care of the rest, maybe that approach would work for you?
Side note, but are you sure eufy doesn’t work without an add-on? It looks to me like that’s what the HACS integration can do (and I have used core in docker for many years before moving to VM; HACS is available even if add-ons are not)?