RPi2: Cannot get onboard ethernet to work on Ubuntu 20.04

[jzdev]

I've been trying to setup Ubuntu Server 20.04 on my old RPi2 but I couldn't seem to get the ethernet port to work. The eth0 keep showing down state I've ran out of idea or general Google support. Hopefully someone here can point me to the right direction to further trouble shoot this issue. Thank you.

Background:
I'm very new to Ubuntu 20.04, I believe since 18 networking needs to be manually configure on netplan.

I've setup the netplan file and have generated and apply the setting, but only the wifi adapter works, wasn't able to get the eth0 to work.

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01-netcfg.yaml
network:
    version: 2
    # renderer: networkd
    renderer: NetworkManager
    ethernets:
      eth0:
        optional: true
        dhcp4: true
    wifis:
      wlan0:
        optional: true
        access-points:
          "ssid":
            password: "wirelesspassword"
        dhcp4: true

Looks like a lot of people got the ethernet logical name wrong, but I've confirm it is eth0.

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ubuntu@ubuntu:~$ sudo lshw -C network
  *-usb:0
       description: Ethernet interface
       product: SMSC9512/9514 Fast Ethernet Adapter
       vendor: Microchip Technology, Inc. (formerly SMSC)
       physical id: 1
       bus info: usb@1:1.1
       logical name: eth0
       version: 2.00
       serial: b8:27:eb:1a:7e:52
       size: 10Mbit/s
       capacity: 100Mbit/s
       capabilities: usb-2.00 ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=smsc95xx driverversion=22-Aug-2005 duplex=half firmware=smsc95xx USB 2.0 Ethernet link=no maxpower=2mA multicast=yes port=MII speed=10Mbit/s
  *-network
       description: Wireless interface
       physical id: 2
       bus info: usb@1:1.5.1
       logical name: wlan0
       serial: 00:0f:60:05:65:5f
       capabilities: ethernet physical wireless
       configuration: broadcast=yes driver=rt2800usb driverversion=5.4.0-1008-raspi firmware=0.36 ip=192.168.1.133 link=yes multicast=yes wireless=IEEE 802.11

Ip link will show the eth0 as down

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ubuntu@ubuntu:~$ ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN mode DEFAULT group default qlen 1000
    link/ether b8:27:eb:1a:7e:52 brd ff:ff:ff:ff:ff:ff
3: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DORMANT group default qlen 1000
    link/ether 00:0f:60:05:65:5f brd ff:ff:ff:ff:ff:ff

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ubuntu@ubuntu:~$ ifconfig
eth0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether b1:22:eb:1b:7e:42  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 1920  bytes 142164 (142.1 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 1920  bytes 142164 (142.1 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.1.xxx  netmask 255.255.255.0  broadcast 192.168.1.255
        inet6 fe80::20f:66ff:fe06:666f  prefixlen 64  scopeid 0x20<link>
        ether 00:0f:66:66:66:5f  txqueuelen 1000  (Ethernet)
        RX packets 3490  bytes 851978 (851.9 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 707  bytes 90662 (90.6 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

I've tried using ifup and ifdown to set the status of eth0, but I get the error below.

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ubuntu@ubuntu:~$ ifup eth0
ifup: unknown interface eth0

I've also set the interface for eth0 for ifup and ifdown.

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/etc/network/interfaces.d/eth0
auto eth0
iface eht0 inet dhcp

[cjan]

no need do anything, default 50-xxx.yaml ethernet work.

[jzdev]

no need do anything, default 50-xxx.yaml ethernet work.

Strangely it wasn't working with the default yaml file, which led me to search for ways to get it to work.