The cable shows 2k @165Hz, but you have a 4k@165Hz… reducing to 4k@100Hz might isn’t enough.
I think you need another cable… but you can try reduce this resolution to 2560x1440 with 100Hz.
I also recommend to buy 1 meter… 1,8meter is probably to long for that bandwith.
Thanks for continue helping me. I don’t have 2560x1440 in the big monitor.
And in my laptop I have this.
Do yo think the long wire can be a problem also if it’s working after load everything?
Thanks
@Kobold Do you think this wire can be ok?
or this one:
Now I have my doubts. I ordered 1.8m because the monitor is big and I’m using my laptop and it’s close to me, I don’t know if 1m will be enough for the distance.
If you confirm me this wires can be ok, I can try to order now and try it tomorrow again
And by the way, this is my monitor:
https://www.mediamarkt.es/es/product/_monitor-34wp75cp-b-lg-34-qhd-1-ms-negro-126312101.html
@Kobold I found in the box of the monitor another wire hidden and is from usb c to usb c. The original of the monitor. But the same, I connected when Manjaro was running and detect the monitor perfectly. I restarted to see if it’s working and same problem, black screen and I need to reset, disconnect the wire, wait until manjaro show my desktop and then yes connect the wire to use the monitor.
So with this new information I’m discarded the problem is the wire, I’m 90% sure is a Manjaro problem or configuration because like I said in my first post with a old monitor vía HDMI I had problems to detect it until I added the line:
optimus-manager.startup=nvidia nvidia_drm.modeset=1
It’s soo weird and annoying me 
It could be both…
TBH im not aware if the USB-C Port from your Laptop can be the limited factor too.
So you used 3440p@60Hz and it worked?
Probably a new cable don’t work… the ugreen cable looks promising to me because it shows display port version 1.4 but i can’t tell if this is working or not sry.
Its also maybe worth to boot from a usb live boot to see if this changed anything.
Check other reviews from your Monitor, if this cable thats in the package included with your Monitor is doing his job or not.
Today there are sometimes just faulty products or bad quality… everything is possible. Its up to you, to check if its worth it to buy another cable.
Another option is maybe to try out your Monitor on another device, maybe if you know a friend who owns a Windows PC. But USB-C is a limited factor here also, Display to Display Port is more common.
Chatgpt told me try with this command:
sudo journalctl -b | grep -i "error"
and I found this information, I don’t know if relevant or not for the problem:
This error is normal, you can try Wayland also… if this changed something, but i don’t have much hope.
No, I was talking about another monitor. Sorry for the confusion.
Yes I have a friend with the same monitor and he told me about the wire that I bought and works perfectly but he uses Windows, not linux.
Oh I hate read that
Then try 1080p@60hz… btw. when your have a black screen, is TTY working?
crlt+alt+f2
I tried to reduce the resolution but it’s working when my laptop is running.
If I restart always is trying to enter in 3440.
If I connect the monitor vía HDMI works perfectly and is detected from the beginning but in 60hz.
I want to use in 160hz because for that I bought
But when your default cable don’t work with 60Hz, maybe its the cable then.
So which res (+60hz) did you used with HDMI?
You always left some information behind 
It could be the USB-C port that has this issue… which HDMI port version is on your Laptop?
no, it’s not working. I tried too is completely black and frozen. The only thing I can do is reset.
And this happen in the beginning if I have the wire connected or if I press restart from the application launcher.
Is like when needs to “connect” or “disconnect” the things (in this case the monitor), fail!
It’s easily reversible and has actually fixed things for a number of people now. Nothing to worry about.
Okay so another HDMI Cable is no solution. But there are still a lot points open, where i pointed at and which you can try.
Switching Wayland in Log-in Menue (bottom left, between X11 and Wayland) and other stuff which i posted above.
I tried to logout session because I have my manjaro with autostart and I realized was again in black screen and now I don’t have connected the monitor. I don’t know why :S
is there another way to init with Wayland? sorry if my questions are basic also I tried to put again the login to write the password on init but I cannot find the option in settings.
I found the option and only with the laptop I changed to wayland, I restarted and I was checking if I’m in wayland or not. I was.
After that I restart again I connected the monitor and again, black screen after the long text of manjaro initialization.
I’m very frustrated really.
Thanks for your patience and continue helping me.
If you have more ideas I can continue testing it.
From my understand your System settings showed X11:
You can do check your system settings again to see the different entry’s.
No problem 
I think you missed some steps or you missed to confirm that they don’t work
(but change back to X11 first):
Yes, this was in the beginning but right now I’m in wayland and is not working.
I will try again maybe in a few hours because I can’t now. But the problem is I can change it right now but when I restart it’s black screen frozen or will init in 160hz and maybe for that it’s frozen. Is like doesn’t save the new config. At least this is what happened last time
Like this right?
I will do it in a few hours and I will keep you informed. Thanks for not abandoning me on this topic! 
