Can't find existing ethernet card after u/d

I did the migration through 16.10 to 17.04. In the process Ubuntu MATE can’t find, or at least, use my existing ethernet card. It was there and working under LST. Now nothing. The good news is I have a working WiFi connection, but oferall, Not Good. Suggestions?

Watched this the other day, maybe this can help with your drivers…
video at correct time for driver talk…

Things are eminently broken. Not only is Ethernet dead, so is audio. I had to go to a Win10 machine to hear the video’s audio. I’d already found my way to Additional Drivers, through Control Center. Additional Drivers only offers "Unknown: Unknown This device is not working (defaults to) “Do not use this device”. Helpful that…

I went through the “no audio” issue with Open SuSE 14.nn. The problem turned out to be audio output was defaulted to HDMI (“why” remains a mystery). Selecting “built-in audio” fixed the problem there. It doesn’t fix it here.

Both Ethernet and audio were fully functional under 16.04 but are now “tango uniform” under 17.04.

Since the primary task for this machine is video editing, this is no small problem.

ADDED: I just figured out that the internal audio is being sent to an optical port (S/PDIF). That would be nice if this tower had one and so did my speakers. I see no clear way to change the audio to analog out.