Yes, the command was diagnostic in nature and I was hoping you would post it so I could see what the root of the problem was. FWIW I think it was the backported libgl1 package but we'll never know now...

Oh!  I thought maybe I irritated someone with my last lengthy log-post, so I didn't even think about saving the output at the time.  My mistake.  But I may end up wiping and conducting a new install yet, anyway, so I'll attempt to repeat the procedure and post it.

Yes, that is a good suggestion.  It doesn't seem to have worked.   I first looked at minimal conf files written from scratch, then I decided I'll copy the one from my successful Xubuntu install that was made on this same box.  The problem has stayed the same, which may mean I either put the file in the wrong place and it's getting ignored, or it didn't really change what needs to be changed.

Running

apt-get -s -o Debug::pkgProblemResolver=yes install nvidia-driver

did result in ... lot's of activity. but then ended with the same group of lines again

Yes, the command was diagnostic in nature and I was hoping you would post it so I could see what the root of the problem was. FWIW I think it was the backported libgl1 package but we'll never know now...

Use an X.Org configuration file.

#oldskool

Oh, and I did have nvidia driver installed using sgfxi for awhile yesterday.  That installed a version 440-something, and it was interesting watching that script resolve a lot of issues as they were encountered.

Yes, that script is very clever at getting nVidia installed and blacklisting nouveau etc.

apt-get -s -o Debug::pkgProblemResolver=yes install nvidia-driver

did result in ... lot's of activity. but then ended with the same group of lines again
starting with

kde-runtime : Depends: plasma-scriptengine-javascript ... (above)

The next suggestion I did was to install using aptitude.  That worked.

sudo dpkg --configure -a
sudo aptitude install nvidia-driver

I was prompted to accept a solution.  And eventually I had a message that said there was a conflict with the nouveau driver, and a reboot would fix it.  I rebooted, and I found that version 390.116 nvidia driver is installed.  Yay

Oh, and I did have nvidia driver installed using sgfxi for awhile yesterday.  That installed a version 440-something, and it was interesting watching that script resolve a lot of issues as they were encountered.

Steve

apt-get -s -o Debug::pkgProblemResolver=yes install nvidia-driver

It should be installable

I could also try installing the driver nvidia has on their web site

If you do that then you will have to rebuild the kernel module manually every time the kernel is updated. The Debian package will do that automatically.

Anyway, I think you just need to update your package database:

# apt update
# apt install nvidia-driver

I am presuming here that you have already installed the kernel headers, either directly or with module-assistant.

steve wrote:

The following packages have unmet dependencies:

Well that's not right

Are your sources still as posted earlier? What does APT think is available?

apt policy

I edit the /etc/apt/sources.list file the same way with every install.
I just verified it.  Using apt policy, APT thinks this is available:

Package files:
 100 /var/lib/dpkg/status
     release a=now
 500 http://us.deb.devuan.org/merged ascii-updates/main amd64 Packages
     release v=2.0.0,o=Devuan,a=stable-updates,n=ascii-updates,l=Devuan,c=main,b=amd64
     origin us.deb.devuan.org
 500 http://us.deb.devuan.org/merged ascii-security/main amd64 Packages
     release v=2.0,o=Devuan,a=stable-security,n=ascii-security,l=Devuan-Security,c=main,b=amd64
     origin us.deb.devuan.org
 500 http://us.deb.devuan.org/merged ascii/main amd64 Packages
     release v=2.1,o=Devuan,a=stable,n=ascii,l=Devuan,c=main,b=amd64
     origin us.deb.devuan.org
Pinned packages:

You could try aptitude instead, it has a more advanced dependency resolution algorithm and should offer several choices.

I could.  I didn't know that was an option.  Thanks.
I could also try installing the driver nvidia has on their web site.  It looked kinda involved, but what I've been doing has been kinda involved.

The following packages have unmet dependencies:

Well that's not right

Are your sources still as posted earlier? What does APT think is available?

apt policy

You could try aptitude instead, it has a more advanced dependency resolution algorithm and should offer several choices.

I didn't read through all the posts and thus don't know if it's related, however, I've had the above (link) 'problem' over and over again when using the repository packed packages of the NVIDIA driver.

Might help,
Olav

On Devuan ASCII

I don't have Bumblebee.
I haven't tried sgfxi as yet.

nvidia-detect
Detected NVIDIA GPUs:
0c:00.0 VGA compatible controller [0300]: NVIDIA Corporation GP104 [GeForce GTX 1070] [10de:1b81] (rev a1)

Checking card:  NVIDIA Corporation GP104 [GeForce GTX 1070] (rev a1)
Your card is supported by the default drivers.
It is recommended to install the
    nvidia-driver
package.

So my card is supported.

sudo apt install nvidia-driver
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 kde-runtime : Depends: plasma-scriptengine-javascript (= 4:16.08.3-2) but it is not going to be installed
               Depends: libkdewebkit5 (>= 4:4.9.95~) but it is not going to be installed
               Depends: libplasma3 (>= 4:4.9.95~) but it is not going to be installed
               Depends: libqtwebkit4 (>= 2.1.0~2011week13) but it is not going to be installed
 kdelibs5-plugins : Depends: libkdewebkit5 (= 4:4.14.26-2) but it is not going to be installed
 konqueror : Depends: dolphin4 (= 4:16.08.3-1) but it is not going to be installed
             Recommends: kpart-webkit but it is not going to be installed
 libgl1 : Depends: libglx0 (= 1.1.0-1~bpo9+1) but it is not going to be installed
E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages

I notice after this that I have the nouveau drivers installed.

I've conducted searches on this forum, and it has occurred to me that maybe I've asked the wrong question.
I've been successful in getting both Ubuntu and Xubunto, both with KDE, running on this system, and both with nvidia drivers 435.21.
My 'clue' for the successful install of the nvidia drivers was going into Display Settings and seeing an additional monitor detected, and having to adjust resolution and such.  With Devuan, I never see the additional monitor being detected, and that was when I assumed that the install to be a failure.
Having saved the Ubuntu and Xubuntu drives, I've gone back and checked them, and one of the things that stands out is that they have rather lengthy xorg.conf files.  I printed hardcopies of those to have for a ready reference, and found them to be identical, and both of them calling for Xinerama.  Huh.  I wouldn't have thought Xinerama was required these days.  Like I keep reading that an xorg.conf isn't needed.  or is very short, like 4 lines.  I don't know how many lines I have, but with the large 12-point bold font I use (having had 2 eye surgeries this year) it seems to be 1.5 pages long.

So my question might be: how do I get the desktop to recognize I have 2 displays?  Or, maybe, How do I install Xinerama?

I notice that the solution someone else used was to change back to xfce.

Steve

/etc/apt/sources.list

Then install

nvidia-detect

  script:

 # apt install nvidia-detect

Run it (as normal user). Here example output:

$ nvidia-detect
Detected NVIDIA GPUs:
02:00.0 VGA compatible controller [0300]: NVIDIA Corporation GF108 [GeForce GT 430] [10de:0de1] (rev a1)
Your card is supported by the default drivers.
It is recommended to install the
    nvidia-driver
package.

Now, install Linux headers for the kernel you are using. If you are using 4.9 Linux kernel in Devuan Ascii:

# apt-get install linux-headers-$(uname -r|sed 's/[^-]*-[^-]*-//')

Then you can install the package:

# apt-get update
# apt-get install nvidia-driver 

Restart your system to enable the nouveau blacklist. This method i used on all my machines.

P.S.

Do not use this method if you have bublebee.