Netplan routing configuration (IPV4) for dual networking interfaces, with one having access to internet other only accessible via local network. This has been tested in Ubuntu server 20.04 and for some reason netplan apply works although netplan try is not working.

netplan_dual_nic.yaml

# Last update 27-10-2021
# network scheme was create using https://netplan.io/reference/
# The following configuration assumes the first interface has internet access
# CIDR calculator https://mxtoolbox.com/subnetcalculator.aspx
network:
  ethernets:
    eno1:
      addresses:
      - xxx.xxx.xxx.xxx/24 #IPV4 address for interface 1
      routes:
        - to: default
          via: xxx.xxx.xxx.xxx #gateway ip for interface 1
          metric: 3
      routing-policy:
        - to: 0.0.0.0/0
          from: xxx.xxx.xxx.xxx/24 #IPV4 address for interface 1
          priority: 100
      link-local: []
      nameservers:
        addresses:
        - 8.8.8.8
        - 8.8.4.4
        search: []
    eno2:
      addresses:
      - xxx.xxx.xxx.xxx/24 #IPV4 address for interface 2
      routes:
        - to: default
          via: xxx.xxx.xxx.xxx #gateway IPV4 address for interface 2
          metric: 6
      routing-policy:
        - to: 0.0.0.0/0
          from: xxx.xxx.xxx.xxx/24 #IPV4 address for interface 2
          priority: 200
      link-local: []
      nameservers:
        addresses:
        - 8.8.8.8
        - 8.8.4.4
        search: []
  version: 2