How to install Nouveau driver on 19.10 and use DisplayLink

Question

I'm trying to get DisplayLink work on Ubuntu 19.10 for the dual DisplayLink i-tec USB3 to Dual-HDMI device (to have 2 external displays by USB3).

I have posted some log and opened an issue at GitHUB. I wrote to the i-tec support and they said:

The issue you are describing may happen if closed/proprietary nVidia drivers are installed.

Indeed, one of my two integrated graphic cards is NVidia (see below), using driver 430.50 which seems to be the proprietary NVIDIA driver:

sudo lshw -c video
  *-display                
       description: VGA compatible controller
       product: GK104M [GeForce GTX 870M]
       vendor: NVIDIA Corporation
       physical id: 0
       bus info: pci@0000:01:00.0
       version: a1
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress vga_controller bus_master cap_list rom
       configuration: driver=nvidia latency=0
       resources: irq:36 memory:f6000000-f6ffffff memory:e0000000-efffffff memory:f0000000-f1ffffff ioport:e000(size=128) memory:f7000000-f707ffff
  *-display
       description: VGA compatible controller
       product: 4th Gen Core Processor Integrated Graphics Controller
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 06
       width: 64 bits
       clock: 33MHz
       capabilities: msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0

I'm trying to install the opensource (nouveau) driver. Hints are welcome on how to do this (I cannot get the good-old "proprietary driver" management GUI). I'd also like to be sure I can revert to NVidia driver if nouveau does not work. I was used to backup /etc/X11/xorg.conf, but such file does not exist in my setup:

/etc/X11# ls
app-defaults  default-display-manager  ja_JP.eucJP  rgb.txt  xkb          Xreset    Xresources  Xsession.d        xsm         Xwrapper.config
cursors       fonts                    ja_JP.UTF-8  xinit    xorg.conf.d  Xreset.d  Xsession    Xsession.options  XvMCConfig

And there is only 20-displaylink.conf in xorg.conf.d. What should I back-up? (In grub, I have an old Ubuntu 18.04 around that I can boot with in case of needs)

Also, one of the alternative scripts (open source DisplayLink for Debian, say link above) says:

Building EVDI kernel module with DKMS
ERROR (code 3): Failed to build evdi/5.2.14. Consult /var/lib/dkms/evdi/5.2.14/build/make.log for details..

Thank you in advance for any hints!

Answer 1

The gcc-9 compiler seemed to be the issue. After the following, compliling EVDI kernel module with DKMS works (both with Debian DisplayLink and official DisplayLink driver): https://bugs.launchpad.net/ubuntu/+source/gcc-9/+bug/1830961 suggests this workaround:

sudo ln -fs gcc-8 /usr/bin/gcc

However, Debian DisplayLink allows to see the screen but not to activate it. Uninstalling it an reinstalling the official DisplayLink driver, it works. (I cannot test with more than a display connected to it at the moment, though). (I guess it should do no harm to revert to gcc-9 if recompiling kernel modules is not needed; but I have not tried).