I have an Odroid running Ubuntu-Mate. Ubuntu is version 20. I don't know how to get the Mate version via the command line.
I'll try to make this short... I used a monitor, keyboard, and mouse to set a static IP address via the GUI and eventually mucked things up so bad that DNS would not work at all. I install pi-hole and messed up its configuration and then uninstalled it, etc... blah blah blah.
So I connected up the monitor, keyboard and mouse again and went back to DHCP and now things are working. BUT... here are my questions:
The file that changed appears to be /etc/NetworkManager/system-connections/Wired connection 1.nmconnection but the Ubuntu internet pages point to things like /etc/netplan. So, my question is, how does the resolver work with Ubuntu-Mate? As I recall, in normal Ubuntu, there are several hops made before the request goes out over the wire. e.g. /etc/resolv.conf points to 127.0.0.53 which (again, as I recall) points to somewhere else which eventually points to the external name server. Has Mate changed some / all of this? etc.
I have no idea. Since you are using 20.04 I think - best suggestion from me would be fresh install of either the 20.04LTS from April 2020 or wait until the new April 2022 LTS release in a few months. Alternatively, install the 21.10 interim release and then upgrade when the 22.04LTS comes out. Too many unknown issues with your installation. Good luck!
The system is, except for the desktop environment, exactly the same as standard (Gnome) Ubuntu.
/etc/netplan/01-network-manager-all.yaml does not do much at all,
it tells the system to leave all networking to network-manager and that's it.
The DNS-resolver is a separate 'service' running in your system and has not much to do with the whole network 'plumbing' . It listens on 127.0.0.53 for DNS-requests and that is about it.
You can, if you wish, add another DNS-resolver and tell networkmanager to use that one instead of the default resolver.
As I recall, in normal Ubuntu, there are several hops made before the request goes out over the wire. e.g. /etc/resolv.conf points to 127.0.0.53 which (again, as I recall) points to somewhere else which eventually points to the external name server. Has Mate changed some / all of this? etc.
No, Ubuntu-MATE follows the standard Ubuntu for all the crucial underlying systems, including networking, so no nasty surprises there
The file that changed appears to be /etc/NetworkManager/system-connections/Wired connection 1.nmconnection
That is indeed the file where the network-manager stores the settings of your wired connection, so that sounds logical.
In that same directory are the settings-files for every systemwide wireless connection, one per file.
