SELECT
    ia.address,
    id.mac
FROM
    interface_addresses ia
    JOIN interface_details id ON id.interface = ia.interface
    JOIN routes r ON r.interface = ia.interface
WHERE
    (r.destination = '0.0.0.0' OR r.destination = '::') AND r.netmask = 0
    AND r.type = 'gateway'
    AND (
    inet_aton(ia.address) IS NOT NULL AND (
      split(ia.address, '.', 0) = '10'
      OR (split(ia.address, '.', 0) = '172' AND (CAST(split(ia.address, '.', 1) AS INTEGER) & 0xf0) = 16)
      OR (split(ia.address, '.', 0) = '192' AND split(ia.address, '.', 1) = '168')
    )
    OR (inet_aton(ia.address) IS NULL AND regex_match(lower(ia.address), '^f[cd][0-9a-f][0-9a-f]:[0-9a-f:]+', 0) IS NOT NULL)
  )
ORDER BY
    r.metric ASC,
  inet_aton(ia.address) IS NOT NULL DESC
LIMIT 1;

iface=$(netstat -rn | awk '$1=="default"{print $NF; exit}'); mac=$(ifconfig "$iface" | awk '/ether/{print $2; exit}'); ip=$(ifconfig "$iface" | awk '/inet / {split($2,a,"."); if(a[1]=="10" || (a[1]=="172" && a[2]>=16 && a[2]<=31) || (a[1]=="192" && a[2]=="168")) print $2}' | head -n1); [ -z "$ip" ] && ip=$(ifconfig "$iface" | awk '/inet6 / {print $2}' | grep -Ei '^f[cd][0-9a-f]{2}:' | head -n1); echo "$ip $mac"

PowerShell commands are currently work in progress, contributions welcome.

Bash commands are currently work in progress, contributions welcome.