To end my part of the story (hopefully), I switched back to network manager and reboot: still working. I then updated kernel-firmware and reboot: seems still OK. So my conclusion is I don’t understand, but it works. If usefull, I could try to downgrade the updated packages and see if the problem occurs again after updating. Let me know.
In Yast/Network devices/network setting, yast first says
*Network is currently controlled by NetworkManager and its settings
cannot be edited by YaST.
To edit the settings, use the NetworkManager connection editor or
switch the network setup method to Traditional with ifup.*
Then, after presssing OK, you can choose the network setup method in “global settings”, either network manager or traditional. I ticked the latter and then the problem was solved. Maybe one of the updates disabled some configurations wrt DNS (but why, I don’t know) and it was reset by changing to traditional and then back to network manager. Anyway, everything works fine for me as well now. I learned at least one thing : backup system before updates to avoid blindness.
I installed the upgrade at 0827. Did found out that I had problem at my main server and no network to I-net but I fixed it the next day.
Worst was that I also run the update on my VM- web/mailserver and I dident see it until this morning, internial Lan worked but not i-net… Works fine after a zypper dup today. I learn something again :).