networking – Configure Netplan for 2 subnets

Wanting to have linux server span both sides of a router. to provide services to home and
vpn connection to a VPS server remotely.

The main router is AT&T issued and cascading router is broken.
Network connections

Main router

adgaurd home at for dns from the home router

linux server

home router
all pc’s and wifi devices.

have 2nd nic interface installed in linux box want to be on the lan side of home router. want to bridge br0 to both and with routing traffic through
it. Whenever connected on lan side of, network suffers, reduction in speed and slows down this network.

I thought disabling dhcp, and not assigning the gateway to would prevent this but
Where am I going wrong or are there any suggestions.

current netplan



enp3s6:    #
    dhcp4: yes
        route-metric: 100
enp2s0:     #cannot get to operate
    dhcp4: no
    addresses: []

version: 2


    interfaces: [enp3s6]
    dhcp4: true