can you provide return info
boot on iso live manjaro ( may you will need to redo a fresh iso )
if needed no splash on boot
you can add theses parameters on boot
“iommu=pt amd-pstate=guided”
open a terminal and a browser on this topic
sudo parted -l
inxi -Mxa ( check for UEFI only )
test -d /sys/firmware/efi && echo efi || echo bios
manjaro-chroot -a
mhwd-kernel -li
pacman -Qs grub
efibootmgr -v
exit