Hello!
So it turns out I don’t have enough space inside of /var/tmp for that, huh. I was counting with the whole root filesystem as available space 
The output of
glxinfo -B | grep -i memory
is
Memory info (GL_NVX_gpu_memory_info):
Dedicated video memory: 8192 MB
Total available memory: 8192 MB
Currently available dedicated video memory: 7603 MB
df -hT
Filesystem Type Size Used Avail Use% Mounted on
devtmpfs devtmpfs 4.0M 0 4.0M 0% /dev
tmpfs tmpfs 7.8G 252M 7.6G 4% /dev/shm
tmpfs tmpfs 3.2G 1.9M 3.2G 1% /run
/dev/nvme0n1p7 xfs 103G 24G 80G 23% /
tmpfs tmpfs 7.8G 9.3M 7.8G 1% /tmp
tmpfs tmpfs 1.6G 120K 1.6G 1% /run/user/1000
For the Nvidia kernel modules I had to enable the usual
nvidia nvidia_modeset nvidia_uvm nvidia_drm
inside of /etc/dracut.conf to even have the Wayland session available on gdm, however df -hT only shows the nvidia kernel module enabled… I have also enabled nvidia-drm.modeset=1and NVreg_PreserveVideoMemoryAllocations=1 inside of /etc/kernel/cmdline but I don’t remember if I was supposed to do that. I’m used to edit mkinitcipio.conf and actually just used dracut and systemd-boot for the first time this week for my recent install. There might be some problem here as well.