GUI works with nomodeset on Live ISO but installed boot gives blank screen

Impressed how late last year I could install NixOS on my newly recovered hardware with KDE which found my three monitors straight off “in order of left to right flow”, which took me ages to later do with Kubuntu and finally Fedora - I was amazed by this new-to-me Linux that I have heard the guys from Linux Unplugged podcast constantly rave about.
At the time I had to bail on Nixos as I have specific, off the top of my head, Red-Hat-ish based setup being Fedora for me, that I eventually went back to Fedora out of urgency.

I now have a Dell Optiplex 7060 Micro here and will be getting a KVM switch for 3 x screens with 3 x PCs, and so want this little humble Dell to be my new pathway into using NixOS alongside everything else I have here (Fedora, Rocky, CentOS, Kubuntu).

Now to my issue - when I install using the Live USB I have to select the “nomodeset” option for install - works perfectly but after the install completes, I get a blank screen and the monitor eventually thinks there is nothing attached so the nice little led goes from blue (connected) to yellow/orange (no body is home).
I can reboot if I Ctrl-Alt F-[number] and Ctr-Alt-Del and on subsequent boot if I edit the nixos boot and place nomodeset at the end, I at least get a console (just like my old UNIX days since 1987)… no gui.

I have added the recommended “boot.kernelParams = [ “nomodeset” ];” in /etc/nixos/configuration.nix, but this seems to be completely ignored and gives me the MIA attitude from the monitor after a minute or so.

The DP based adaptors in the Dell are based on the following config:

Intel CoffeeLake-S GT2 [UHD Graphics 630]

and although I can’t ‘see’ this being NVidia, any other bits on-line seem to talk about i915 and NVidia in the same discussion.

I have tried at install, the desktop options Plasma, Plasma5 and Gnome all with the same result so does not seem to be related to X environment desktop manager, but more so at the kernel driver level?

As a test on this Dell, I have been able to get Kubuntu 24.04 running but in the GRUB I needed this:


which does give me the KDE GUI on boot and auto-login… so if I can find the correct way to get NixOS to do this, I will be a very happy little chap indeed.
Love the thought of getting familiar with a ground-up developed Linux rather than the respective spin-offs in our industry (I don’t have any issue with these said spin-offs, it is just good to challenge oneself to new OS environments where possible).
Hoping someone can provide some pointers so I can stay with this new ‘to me’ Linux, as I am really impressed by all experience with it so far. Many thanks in advance.

Okay progress albeit strange. Seems to require one to do a:

nixos-rebuild switch

… so forgive my newness to NixOS, I will remember to do this any time I alter /etc/nixos/configuration.nix as this got the boot to include the entry:

boot.kernelParams = [ “nomodeset” ];

It now boots to a ‘console’ based ASCII screen by default rather than a blank screen (thanks to nomodeset). If I then login as my user and do a sudo based “kill” command on the PID for sddm the GUI starts and I am now logging in using the KDE Plasma desktop. I had to use kill as there does not appear to be a restart option in its --help and sddm is not part of systemctl (which may actually be the issue???).

As I don’t intend to do much rebooting of this new little Dell addition I ‘can’ put myself through this each time but as with all things Linux, automation of processes are key/preferred.