Some systems has a nasty habit of losing access to the firmware after your Linux installation. A couple of examples
This document is a work-in-progress ...
It is not clear what makes this happen - a lot is pointing to bad implementations of the UEFI specification - in some cases the firmware is hardcoded to load
Your system will usually be able to boot your installed Linux - only the firmware is not displaying correctly.
Usually you should be able to load the firmware on next reboot by using
$ systemctl reboot --firmware-setup
The first attempt to cure would be to reinstall grub - for an EFI system it goes like this
ESP=$(lsblk -no MOUNTPOINT | grep -e 'efi') sudo grub-install --trage=x86_64-efi --efi-directory=$ESP bootloader-id=Manjaro --recheck sudo grub-mkconfig -o /boot/grub/grub.cfg sudo mkinitcpio -P
Next step is to check with LVFS if your firmware can be updated using Linux
Use https://fwupd.org to get familiar with the Linux Vendor Firmware Service. You can also search the database to verify if your system is supported.
There is no one-size-fits-all answer - the following is a list compiled from Manjaro Forum and the first being from Arch Wiki.
I am listing the possibilities from least to most intrusive action.
su -- provide the root password when requisted
$esp/EFI/Manjaro/grubx64.efi- rename the file or move it to another location