On the old PC:
sudo mhwd -r pci video-linux
you don’t need nouveau on the new PC since it has no nvidia. I’d reboot too even if that boots into a black screen. (If you have a bios option to switch to the integrated intel card it should still boot.)
Then move the drive over to the new PC. If you get a black screen open tty and run:
sudo mhwd -a pci free 0300
I still get a black screen on the new PC.
sudo mhwd -a pci free 0300 will install video-linux. I will move the SSD to the new PC and try
> Using config 'video-linux' for device: 0000:01:00.0 (0300:10de:0de9) Display controller nVidia Corporation GF108M [GeForce GT 620M/630M/635M/640M LE]
> Using config 'video-linux' for device: 0000:00:02.0 (0300:8086:0166) Display controller Intel Corporation 3rd Gen Core processor Graphics Controller
> Installing video-linux...
> Successfully installed video-linux
mhwd = manjaro hardware detection which means it detects the hardware on the PC that it’s running on. So if on the new PC
that’s ok since it’s installing the open source drivers for the hardware it detected, so go ahead and then reboot.
Few minutes has passed. it seems like it is still a black screen.
This is a screenshot of the hardware configuration on LiveISO on the new PC. Seems like video-linux should work as it is the driver that drives the the display of the new PC.
Yes but those are the drivers that come with the liveISO not the ones on the drive!
On the new PC:
Initially on new PC, grub did appear for OS selection. It stucked at black screen after OS selection.
I tried repair the grub according to the following page on a liveISO on the new PC.
End up, the SDD is no longer bootable.
error: symbol 'grub_is_lockdown' not found.
Entering rescue mode...
grub rescue>
Update:
I booted LiveISO on my old PC, chroot and repaired my portable SSD manjaro. Now the system can be booted properly on my old PC. However, on the new PC it cannot be booted. It still gets into the grub rescue mode with the same error message as above. I tried repair it again with LiveISO on the new PC but it doesn’t help.
is secure boot disabled in bios in the new pc?
is fast boot disabled - you may not have this option;
is it in AHCI or RAID mode?
is there windows installed? if yes, does it have fast startup disabled?
is the new pc in uefi/GPT mode and the SSD in MBR/bios mode? or vice-versa?
is secure boot disabled in bios in the new pc? Yes, disabled
is fast boot disabled - you may not have this option; Yes, disabled
is it in AHCI or RAID mode? SATA mode on the new PC is AHCI
is there windows installed? if yes, does it have fast startup disabled? Yes, old PC is win10 and new PC is win11. fast startup disabled
is the new pc in uefi/GPT mode and the SSD in MBR/bios mode? or vice-versa? both PC are in UEFI. SSD should be installed in UEFI mode as it was installed using the old PC. is there a way to double confirm that?
update:
yes. after checked with parted -l, my SSD is GPT.
sudo parted -l
For example tells if gpt or mbr.
Thanks a lot. My SSD is GPT.
Just for fun, try the following… 
sudo grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=manjaro --recheck --removable
sudo update-grub
Thanks for the suggestion. I have actually tried that based on this page GRUB/Restore the GRUB Bootloader - Manjaro , but it didn’t help. After trying that, the SSD is not no longer boot into a black screen but into grub rescue mode.
https://forum.manjaro.org/t/portable-manjaro-ssd-boot-into-black-screen-on-vivobook-15x/146339/27?u=sweizhong