Latency Test OK, dennoch Fehlermeldung

 PCW, Tommylight: I deleted the 10.10.10.1 gateway entry and the "IPV4 Addressierung". Both has no effect for the connections.
Chris(at)cnc: I tried your interfaces file - after restart I have no connections anymore.

So, I think I should give it up. I go with the status quo and start with manually configured connections as before, in network manager.
I would like to have a starter file on my desktop, with the ethtool line.
Can you help me to create that batch with sudo ethtool -C eno1 rx-usecs 0 ? I created a file called ethtool.sh, but I can't start it with double-click.
Then, I created a starter file with  Exec=konsole --hold -e bash /home/hanno/Schreibtisch/ethtool.sh but that doesn't work. I found that line in a forum posting but I dont have the slightest idea from that...

Thanks for all your help!
Hanno

New install.
Did not want to say this often, but from experience i know playing with network manager and etc/network/interfaces file usually can not be recovered easily, as those are also tied to other networking stuff in Linux.

Hello tommylight! I know, you said this somewhere at the beginning of this thread. I must say, I did not know anything about the fickleness of this theme. I am (now as before) absolute newbie to Linux and Linuxcnc, I made my config with the wizard and afaik, I did not touch the /etc/network files at any time until someone in this thread told me to do this. I did not play around with settings but tried to consolidate the network with the help of the guys here. If I have done sth. wrong, I apologize.

Any help with my latest questions (bash) is welcome.

Cheers, Hanno

Sorry but i can not help you with stuff i have no clue about, the bash is trying to run an executable file that i do not know what it contains, etc, etc.
I do admire your will to try and fix it and you being hell bent on learning new stuff, but at some point you have to cut the losses and move on.
Find another hard drive, cheap used one, install everything you need, and if this succeeds, then get rid of the old one. This way you still have a backup.