It means the instigator of the problem is not Plymouth boot splash.
You could maybe use TTY or runlevel 3 to get further in the boot but without GFX at all.
If you cannot gain access with the existing/internal system then you can use a live ISO and chroot into it.
I have the same issue as described using kde plasma desktop. However if I did an install using Cinnamon as the only desktop then there was no problem on start-up. I then installed while the machine was running Cinnamon the kde plasma desktop meta package and could log out of Cinnamon and then come back in using the kde plasma desktop which ran OK. However once the Plasma desktop has been used, even if afterwards you set the desktop back to Cinnamon at the log on screen, then a reboot and the stop came at ‘Reached target Graphical Interface’ visible having disabled Plymouth in order to see what the console describes.
With an Alt F2 tp pick up a terminal and logging in as root and doing dmesg shows a first lightdm (9512) segfault as the last but two records before the hang as likely cause in libglib-2.0.so.0 on CPU 0 core 0 Socket 0 and a second lightdm (9917) segfault in libc.so likely on CPU 1 core 0 socket 1 and a final one suggesting lightdm (19298) libc.so again likely on CPU 3 core 0 socket 3. Processor is an AMD Ryzen 5.
Unable to cut and paste the last of the dmesg but have recorded it as a screenshot should a dev ask for it.
I am running in KVM but since the OP did not describe a VM (Virtual Machine) I doubt that using a VM is contributing to the issue. It looks like lightdm has problems either internally or externally if there is a kde plasma desktop that has been used in the past.
I now have a workaround to this problem. Replace the display manager (dm) lightdm. I used SDDM instead which is in the repos.
Once SDDM is installed it can be activated with the command:
sudo systemctl enable sddm.service -f
The -f will stop the existing dm however if you want to be 100% sure that lightdm is stopped for good use this first
sudo systemctl disable lightdm.service
Because the bug as described by the OP stops one getting to the graphical desktop, when the machine hangs with the segfaults on lightdm use ALT F2 to get a terminal prompt log in (if you log in as root you will not need the sudo in the commands) and issue the above commands. To install SDDM at the prompt first if not already installed all you need is:
sudo pacman -S SDDM
Hope this helps as a workaround while lightdm gets fixed.
If i may, i had this same issue today, it’s certainly related to the update of QT6. Did OP do an update recently ? if so you need to run sudo pacman -Syu
This should fix your issue, as it did mine. if not maybe do a snapshot rollback with snapper and then proceed with a new update. The important part has to be that plasma-integration & plasma-workspace have to update alongside QT6.
First have you installed sddm - sudo apt install sddm
Then have you stopped the existing display manager? Which I assume from the problem is lightdm - sudo systemctl stop lightdm
Finally you can do
system enable sddm.service -f
On a terminal it will then show you that it has rewritten the symlink for the displaymanager to point at sddm instead of lightdm
Then you can reboot.
All this can be done from the point of being halted at the running hook [plymouth] message. It is only the display manager that is stuck you do have consoles running so the usual command to bring up a terminal where you can log in and issue the commands without needing a GUI running is Ctrl Alt F2. Ctrl and Alt held down while tapping function key F2. For reference the Plymouth message is on Ctrl Alt F1 and your GUI when it is running is on Ctrl Alt F7.
The problem causes lightdm to seg fault and appears qt6 may be the root cause. Sddm instead of lightdm is the workaround for the moment.
There are generic on-line guides on how to swap out the display manager and while they may not reference CachyOS directly they do work OK.
Hopefully all will be well soon, and you will be enjoying cachyOS.
And these other posts necrobumping* an unrelated thread* are in relation to the recent scenario of some users upgrading parts of QT6 before parts of Plasma or SDDM or some others.
My bad, sorry about that I meant pacman -S of course. I was busy doing an aarch64 Debian system when I typed the last hence apt install when I should have written pacman -S. Age is catching up with me!
I replaced lightdm with sddm about three weeks ago and all cachyos upgrades since have been perfect. Cachyos has not missed a beat since swapping the display manager to sddm. I have latest Plasma 6.5.3 after two upgrades, Gnome and Cinnamon as desktops, so sddm is getting a fuil workout. If you want remote control of mouse and keyboard (like from a laptop the other side of the room) check out deskflow. Perfect to control a media machine across the room from a laptop on the sofa.