I'm sorry if I was rude; it wasn't my intention.
I've also tried a gnome live disk, and I've encountered the same problem.
I initially tried with dragonized, but the gnome edition made no difference, as I wrote above.
Unrelated to the actual issue, but I'd urge you to clean that screen! 
Related to this issue (teasing Dragonfire lolll), it's not that the visible screen is cut in half, it's that the resolution is shrunk to half your screen as if you had a screen that is physically half the real one.
Sounds like something is badly configured or detected somewhere...
I may not give you much details about it, but I will give you a direction: looking at all your Xorg configurations and trying to see if something can be changed there to improve or fix it. That would be the first place I would try something as it's easily "rollbackable" if it doesn't work.
I assume you could also try to force a PERMANENT modeline in xorg.conf (or monitor.conf or whichever xorg configuration like 20-amdgpu.conf or 20-nvidia-conf or anything there). It could look like this:
Section "Monitor"
Identifier "DisplayPort-0"
Modeline "3840x2560_60.00" 847.25 3840 4160 4584 5328 2560 2563 2573 2651 -hsync +vsync
EndSection
Edit IDENTIFIER to match yours.
Edit MODELINE to match the resolution you want. I am using cvt to get the values from the resolution I want, like this:
─λ cvt -v 1280 1024
# 1280x1024 59.89 Hz (CVT 1.31M4) hsync: 63.67 kHz; pclk: 109.00 MHz
Modeline "1280x1024_60.00" 109.00 1280 1368 1496 1712 1024 1027 1034 1063 -hsync +vsync
But FIRST, try the non-permanent solution by replacing the above 1280 1024 with the resolution you used with cvt and copy the entire Modeline line in clipboard EXCEPT the word "Modeline".
Then do
xrandr --newmode "1280x1024_60.00" 109.00 1280 1368 1496 1712 1024 1027 1034 1063 -hsync +vsync
using your values.
Next you create a new xrandr mode:
xrandr --newmode "1280x1024_60.00" 109.00 1280 1368 1496 1712 1024 1027 1034 1063 -hsync +vsync
Last step is to add the new resolution to OUTPUT. Use just the name of the mode, since the parameters have been set previously:
xrandr --addmode "OUTPUT" 1280x1024_60.00
Change the resolution of the OUTPUT to the one has been defined:
xrandr --output YOUR_OUTPUT (like VGA1, etc.) --mode 1280x1024_60.00
If you want to read about this go here: Guide to X11/Define new resolution - Wikibooks, open books for an open world
You have to make sure to get the resolution right to match the entire screen. If something breaks and you can't revert, then that's my fault, I am the only one to blame and you will have to find a way to reboot (plz make backups and/or snapshots before testing). However the above is NOT permanent, so a reboot will clear whatever broke.
If you wish to make permanent cuz it solved the issue, then we'll get into that later, although you have the answer in the above URL. 
Once the command was done, the screen went black, and even restarting did not solve it. I had to use a snapshot to revert that command, so to me, it seems permanent 
Wow that was unexpected! The worst part is I tested it before... There is something quite wrong somewhere, maybe that "thing" cause it to fail bad on your laptop. 
Sorry about that.
You made sure you used your correct Identifier in the last xrandr command? DP-0, HDMI-1, other....
I used eDP-1
xrandr --listactivemonitors
Monitors: 1
0: +*eDP-1 1920/309x1080/174+0+0 eDP-1
Sounds about right.
Your rez shown in the above command looks normal as well.
Xorg uses different configs for display, 2 of them are: Screen and Monitor.
I am not good enough to tell more, if I were to have such an issue I would first swear, then I'd try a bunch of things for Screen section and Monitor section in the Xorg config. But I'd have to read a lot of web pages to give me ideas of what to try, cuz as I said I am not good enough to think of something without help.
If anyone finds a solution for your issue, I will learn from it too.
When I did that command, the refresh rate was set to 144hz, so the problem wasn’t there.
The problem is present only at 60hz.
EDIT: I just tried to redo the command at 60hz, and the output is the same
Can you confirm you try to use a resolution that is listed in
grep Modeline /var/log/Xorg.0.log
… silence …
Time has passed without significant outcome.
You did not ask your vendor.
You did not check your HW user manual and give details.
The same issue happens on other Live ISO.
This issue is solved!
Case closed.
If you find any other solution than that 
, send a PM to any moderator to re-open this topic.
After extended investigation, it seems more likely a hardware/firmware failure.