GTX970 with Realtek driver,no sound... fresh install

First of all, welcome to the community, my friend.

So you're have difficulty with sound, eh? The first thing to try would be alsamixer. Enter 'alsamixer' in your terminal and increase the volume for each bar. You might have to install alsamixer. Although given that you know enough to try 'aplay -l', I suppose you may have already tried all this, just didn't mention it in your original post.

I'm ruing a slowly aging GTX 560 Ti. I can very easily toggle between HDMI (my GPU) and Analog Output (mobo) from Gnome's All Settings menu which you can find by clicking the top right coer of your desktop, navigating down the the wrench and screw driver icon and then under 'Hardware', click, 'Sound.' You should have something which looks like what i've attached. From there you can choose to enable and disable what ever audio devices were auto detected by Ubuntu. You can also try adjusting the volume from this Sound menu.