SUMMARY
Completely fresh install of Arch (6.11.3) with KDE Plasma 6.2.1. My system has 2 GPU's (A770 and RTX3090). The 3090 is isolated at boot (vfio-pci is using it) for VM pass-trough. KDE is using Intel A770 which is confirmed by nvtop, all processes run on A770. I have 2 monitors connected to that GPU via Display Port. At the first glance everything works fine, but when I drag a window while holding L-SHIFT KDE doesn't display the box where it will position the window in the grid (tile). When I let go the mouse button it DOES tile the window but there's no visual effect when moving the window around (the blue box highlighting the position). Same happens when I drag a window to the edge. Usually you'll get a highlighted box showing you where the window will be if you let go of the mouse button, but KDE is displaying nothing, it does drop (resize) the window but doesn't draw anything on the screen beforehand.

Journal is getting spammed by:
kwin_scene_opengl: 0x1: GL_INVALID_OPERATION in glDrawBuffers(unsupported buffer GL_BACK_LEFT)

While I press L_SHIFT and drag a window I'm getting probably 10 of those per second. Same happens when I drag a window to the edge, and also when I press SHIFT+TAB. All packages on my system are up-to-date. I tried to downgrade kwin, but it didn't help.

What's really odd is I had this exact setup running previously without any issues. I decided to upgrade my boot NVMe SSD to a larger one, and did a fresh install of Arch/KDE yesterday. All I changed in the system was the drive, nothing else, and now I'm getting those errors all of the sudden. And the errors in journal really don't bother me much as the lack of visual cues when I'm dragging (tiling) windows around.

STEPS TO REPRODUCE
1.  Press and hold L-SHIFT and drag around window.
2.  Press ALT+TAB.
3.  Drag a window to the edge of screen.

OBSERVED RESULT
No visual confirmation. KDE doesn't draw the blue box(es) on the screen.

EXPECTED RESULT
When you move the windows around with L-SHIFT pressed it should draw blue boxes showing the user where the window is going to end up in the grid. Same with dragging the window to the edge, but it doesn't.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma:  Arch 6.11.3-arch1-1
KDE Plasma Version:  6.2.1
KDE Frameworks Version: 6.7.0
Qt Version: 6.8.0

ADDITIONAL INFORMATION
Full kinfo:
Operating System: Arch Linux 
KDE Plasma Version: 6.2.1
KDE Frameworks Version: 6.7.0
Qt Version: 6.8.0
Kernel Version: 6.11.3-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 24 × Intel® Core™ i9-14900K
Memory: 94.1 GiB of RAM
Graphics Processor: Mesa Intel® Arc

Journal message:
10/17/24, 19:03:45
kwin_wayland
kwin_scene_opengl: 0x1: GL_INVALID_OPERATION in glDrawBuffers(unsupported buffer GL_BACK_LEFT)
journal
PRIORITY	4
CODE_FUNC	unknown
CODE_LINE	0
CODE_FILE	unknown
SYSLOG_IDENTIFIER	kwin_wayland
_TRANSPORT	journal
_UID	1000
_GID	1000
_COMM	kwin_wayland
_EXE	/usr/bin/kwin_wayland
_CAP_EFFECTIVE	800000
_AUDIT_SESSION	2
_AUDIT_LOGINUID	1000
_SYSTEMD_CGROUP	/user.slice/user-1000.slice/user@1000.service/session.slice/plasma-kwin_wayland.service
_SYSTEMD_OWNER_UID	1000
_SYSTEMD_UNIT	user@1000.service
_SYSTEMD_USER_UNIT	plasma-kwin_wayland.service
_SYSTEMD_SLICE	user-1000.slice
_SYSTEMD_USER_SLICE	session.slice
_MACHINE_ID	994b904a6bdd4bfb9d0501bad238e8d7
_HOSTNAME	archlinux
_RUNTIME_SCOPE	system
MESSAGE	kwin_scene_opengl: 0x1: GL_INVALID_OPERATION in glDrawBuffers(unsupported buffer GL_BACK_LEFT)
QT_CATEGORY	kwin_scene_opengl
_BOOT_ID	46ad8ceff09b4ff5b83bf790fe431eb9
_PID	902
_CMDLINE	/usr/bin/kwin_wayland --wayland-fd 7 --socket wayland-0 --xwayland-fd 8 --xwayland-fd 9 --xwayland-display :0 --xwayland-xauthority /run/user/1000/xauth_WqlzHI --xwayland
_SYSTEMD_INVOCATION_ID	427d32a879d7480da834524586fd47c5
_SOURCE_REALTIME_TIMESTAMP	1729206225195060