Hello,
Changed my laptop from HP to Dell N5110 with Nvidia G525M.
Installed all updates.
My external monitor (HDMI) didn't get detected at all, installed the driver via DoFlicky and rebooted to encounter a black screen and blinking dash.
I did the below to login again.

  1. Started TTY and reversed the driver installation via sudo eopkg history - t (Number)
  2. Restarted GDM via systemctl restart gdm

DE: gnome

PS: searched the forums with no benefit.

    KingLucius Which driver version did it install?

    From NVIDIA's web page it seems nvidia-390-glx-driver-current is the appropriate driver.

      Justin that's what DoFlicky suggest and installed, right after reboot just black screen with blinking dash.

        KingLucius Is this a dual-boot/multi-boot situation? Specifically, is Windows also installed on the same machine?

          inkbug Yes, W10 dual boot installed to the same HDD in another partition of course.

          By the way, if there is any way to get my HDMI external screen to be detected without driver installing will be great as I don't game at all.

          Update:

          Now it boots to Grey screen after blinking dash for some seconds.

          While I am on this Grey screen I pressed "enter" typed my login password then "enter" now I have the wallpaper with the mouse courser without anything else

          Sometimes this could occur if you install a driver on a system that is not fully up-to-date.

            kyrios Is there any hack to get my hdmi detected without Nvidia driver ? I don't need this driver as I don't game at all

              kyrios I spent the day googling without any success 😀 Can you help me with more details if you can?
              Thanks in advance.

                KingLucius I don't have a HDMI monitor or TV, (my TV set is still a 60kg CRT) and I don't have the same GPU as you do.

                All I can advise if you have problem with HDMI is to first boot, update your system, etc. without connecting the monitor, then when everything is up-to-date and working fine, you can try to connect it and reboot.

                If you install the nvidia drivers, make sure DoFlicky selects the nvidia-390-glx-driver

                Personally when I do a google search, I found plenty of results with nouveau not detecting HDMI monitors and many of them are SOLVED, I am pretty sure some of the solutions should work for you since nouveau does support HDMI.

                OK this is half-solved case so far 😃
                I noticed that the monitor got detected with model name and other details using journalctl | grep NOUVEAU but xrandr didn't detect HDMI as an output and after googling I found out that I have to relay the HDMI port that is hard-wired to the Nvidia card to be readed using Nouveau by using:
                xrandr --setprovideroutputsource 1 0
                After that xrandr will detect HDMI then:
                xrandr --output HDMI-1 --auto will make the signal appear on monitor.

                PS: there is a kernel bug that prevents sound:
                https://bugzilla.kernel.org/show_bug.cgi?id=207223

                The performance is so buggy and currently I'm searching for the reasons.

                  KingLucius Does this mean you removed the nvidia-390-glx-driver, and that now your system, though buggy, gets past the blinking-cursor-on-black screen stage, and boots into the gnome de?

                    inkbug I removed Nvidia 390 driver because I couldn't figure out how to pass the black screen.
                    BTW I noticed that in case installing 390 driver with 32 support the black screen go away and was just a Grey color screen (like gnome login background) without anything else showed, but if you pressed "enter" then typed your login and enter again (login process) the wallpaper appear and mouse only.

                    Anyway, I couldn't get Nvidia driver to work good so I turned to getting hdmi work with Nouveau (as it boots fine)
                    Now the hdmi is so buggy (in general) and when it work it's very slow while in "external only" mode.
                    I googled it and it seems it's something with vsync. I will try and feed you back.

                    Ok here is the final solution.

                    From the start when installing Nvidia drivers it goes to black screen and blinking dash, but if you wait about one minute if turns to just grey screen (Login background color) and when you imitate the login process the wallpaper and mouse appears. What I figured out that everything is working as it should it's only about the primary monitor !! the system is working good but showing everything on another (virtual monitor) !! after a lot of tried via xrandr to make my laptop screen primary with no result.
                    I used the tip in this bug report:
                    https://gitlab.gnome.org/GNOME/gdm/-/issues/372

                    1. Configure your desktop the way you want.
                    2. sudo cp ~/.config/monitors.xml ~gdm/.config/
                    3. Edit ~gdm/.config/monitors.xml to make sure the monitor you want as primary is set as <primary>yes</primary>

                    After rebooting everything login appeared on my laptop screen and HDMI worked and the performance is way better and stable than Nouveau.
                    Thanks and this thread can consider ass Solved.