You’re right about that too, the only HDMI cables I have are those old cable you keep in a shoe box 
That’s the reason I use the DP to HDMI cable which is the newest I bought.
I’ll try the HDMI cables I have asap.
I can relate so much 
None of the HDMI cables I have allow me to get 100Hz.
But after few days with a really usable desktop experience at 50Hz make so much the difference comparing to the previous months … I give up for the 100Hz 
Thanks again for your help 
maybe check if your monitor doesn’t have a knob to enable 100 Hz
No, there is nothing on the monitor for that.
I have the 50Hz cap on my desktop (NixOS 23.10 + Nvidia), and not on my laptop (NixOS 23.05 + Intel+Nvidia).
In addition, for another problem, I just booted a Ubuntu 23.10.1 Live USB and my monitor worked quite well with nouveau driver. I checked and I had the 100Hz option: Pasteboard - Uploaded Image
I guess I now need to test the nouveau driver on my desktop, just to see if I get the same values as Ubuntu or not … then I could try Ubuntu + nvidia, which means I need to install Ubuntu on a drive … I’m not shure i’ll do this last one step
Could you try with a NixOS liveCD ? (the plasma or gnome installer 
)
I will, but first, I wanted to try my nixos 23.11 with nouveau driver.
Because since I found the root cause of my problems in my motherboard bios, I wanted to retry nouveau.
Everything runs fine.
In get like on Ubuntu the extra framerates in my settings, by default I’m ~60Hz
I can choose 99.98Hz, but applying this framerate does not work … the screen turns off. (and for the record my laptop show 100Hz and it works)
After playing a little with wayland + nouveau, I find it more usable than wayland + nvidia.
For example, in Gimp (flatpak), some menues are flickering with wayland + nvidia.
Which made me prefer xorg + nvidia over wayland + nvidia.
I’ll give a try with wayland + nouveau, and then xorg + nouveau to get more details…
But for the framerate … the mystery is not solved yet
The big problem with running nouveau long-term is that it effectively has no power/frequency management for most nvidia GPUs.You’ll be running your GPU at 100% frequency all the time, with no boosting available.
This results in poor performance in more intensive applications (since boosting is not available, and overall I believe nouveau runs things at a lower frequency), and terrible power efficiency.
For the GPUs that have support, it’s quite new, like, last couple of months new, so YMMV
Yeah, this is because nvidia’s driver is not a mesa driver, and nvidia have been dragging their feet around wayland support. To prevent that flickering wayland needs to implement something they call explicit sync, I’d estimate that’s about a year or so away.
Before that, using nvidia’s drivers will result in flickering in all xwayland applications, at least. Gimp should support rendering on wayland natively, though, so maybe try that, I think the flatpak uses X by default.
The current latest nvidia driver is also horribly buggy, especially on wayland, so maybe you’re running into their driver bugs…
Thanks for the detailed explanations @TLATER
I’m going to stick with nvidia drivers and xorg then.
Nvidia because Gnome with nouveau is not as fluid as nvidia, even if the framerate is better (60Hz max with nouveau, 50Hz with Nvidia). For example, when you click Super on Gnome, the “Expose-like” mode is laggy.