Hello,

I just made my release upgrade (in graphical mode) from KDE neon Ubuntu 18.04 to version 20.04. After rebooting and passing a few minutes under Windows, I noticed that I lost the network under KDE neon. I rebooted in recovery mode, with the previous kernel, and now, when I try to activate the network, it doesn't work any better.
- I did a sudo apt install -f
- I did a sudo dpkg --configure -a
- I reboot the box
- no need to worry about connecting from another PC in the network, nor from Windows on the stranded PC
- I can't access the box from my neon KDE, but I can access it from Windows (192.168.1.1)

Last night, it resolved "by itself", I had nothing more time to do, except document myself. Probably a DHCP problem, but I checked in my box, under Windows.

I don't know what to do...

Any ideas? Thank you.

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$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether bc:ee:7b:5d:67:ea brd ff:ff:ff:ff:ff:ff
    inet6 fe80::2552:d3aa:fc46:cbb4/64 scope link noprefixroute
       valid_lft forever preferred_lft forever
3: wlp3s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
    link/ether 24:0a:64:54:ff:10 brd ff:ff:ff:ff:ff:ff

//EDIT: two error messages are displayed while the temptation to connect loops:

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$ cat /etc/network/interfaces
# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

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$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether bc:ee:7b:5d:67:ea brd ff:ff:ff:ff:ff:ff
    inet6 fe80::2552:d3aa:fc46:cbb4/64 scope link noprefixroute
       valid_lft forever preferred_lft forever
3: wlp3s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
    link/ether 24:0a:64:54:ff:10 brd ff:ff:ff:ff:ff:ff

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$ sudo nmcli con add type ethernet con-name filaire ifname eno1 ip4 192.168.1.21/24 gw4 192.168.1.1
[sudo] Mot de passe de patrice :
Connexion « filaire » (e856f7f6-b3d0-485c-9b81-1b5cbb62324f) ajoutée avec succès.

$ nmcli g
STATE                      CONNECTIVITY  WIFI-HW  WIFI    WWAN-HW  WWAN   
connecté (site seulement)  limité        activé   activé  activé   activé

$ nmcli device status
DEVICE          TYPE      STATE       CONNECTION
eno1            ethernet  connecté    filaire   
wlp3s0          wifi      déconnecté  --         
p2p-dev-wlp3s0  wifi-p2p  déconnecté  --         
lo              loopback  non-géré    --

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$ ping 192.168.1.1
PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
From 192.168.1.21 icmp_seq=5 Destination Host Unreachable
From 192.168.1.21 icmp_seq=6 Destination Host Unreachable
From 192.168.1.21 icmp_seq=7 Destination Host Unreachable
From 192.168.1.21 icmp_seq=17 Destination Host Unreachable
From 192.168.1.21 icmp_seq=18 Destination Host Unreachable
From 192.168.1.21 icmp_seq=19 Destination Host Unreachable
^C
--- 192.168.1.1 ping statistics ---
22 packets transmitted, 0 received, +6 errors, 100% packet loss, time 21491ms
pipe 4

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$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether bc:ee:7b:5d:67:ea brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.21/24 brd 192.168.1.255 scope global noprefixroute eno1
       valid_lft forever preferred_lft forever
    inet6 fe80::d349:60cb:4424:bc90/64 scope link noprefixroute
       valid_lft forever preferred_lft forever
3: wlp3s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
    link/ether 24:0a:64:54:ff:10 brd ff:ff:ff:ff:ff:ff

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