I am amazed by your post! Yesterday I felt so desperate and now I see the light of hope. Thank you so much already!
In light of your problem, how did you install the kernel?
I installed the Kernel by the console as it failed with the GUI. For this I followed this
sudo mhwd-kernel -i linux54
That shouldn’t have been needed, because in Manjaro,
/etc/mtabalready is a symlink to/proc/self/mounts.
Yesterday nothing seemed to work and I did this because I got the following the same error output as in this thread:
Boot up with the working 4.19 kernel and post the output of…
➜ ~ ls -l /boot
total 94364
drwxr-xr-x 3 root root 4096 Jan 1 1970 efi
drwxr-xr-x 5 root root 4096 Nov 11 17:12 grub
-rw-r--r-- 1 root root 30021916 Nov 6 17:43 initramfs-4.19-x86_64-fallback.img
-rw-r--r-- 1 root root 10071733 Nov 6 17:42 initramfs-4.19-x86_64.img
-rw-r--r-- 1 root root 31171951 Nov 11 17:12 initramfs-5.4-x86_64-fallback.img
-rw-r--r-- 1 root root 9668249 Nov 11 17:12 initramfs-5.4-x86_64.img
-rw-r--r-- 1 root root 3161088 Jun 16 19:50 intel-ucode.img
-rw-r--r-- 1 root root 23 Oct 30 11:24 linux419-x86_64.kver
-rw-r--r-- 1 root root 21 Nov 1 14:42 linux54-x86_64.kver
drwxr-xr-x 2 root root 4096 Jun 4 16:34 memtest86+
-rw-r--r-- 1 root root 6002496 Nov 6 17:42 vmlinuz-4.19-x86_64
-rw-r--r-- 1 root root 6498624 Nov 11 17:12 vmlinuz-5.4-x86_64