I have successfully install Manjaro on a USB3 drive.
At this point, when I boot, I’m presented with the boot screen and the option to boot Manjaro (from the external drive) or Unbuntu (from the internal drive.)
The actual drives are the same form factor.
Can I replace the internal with the external? (So, I would remove the external drive from it’s USB enclosure and put it in place of the internal drive.)
Is there going to be trouble ahead?
Is there a process I should follow that would update the grub/boot etc.?
If both drives have an EFI system partition, then it should in theory work, although you may have to reconfigure the efivars. Considering the drive swap, this is then best done from the install medium in live mode. See…
I read the man page for efibootmgr. But, I wasn’t clear on how if I booted live from the install media I could tell it to act on the boot info on another device. I might have missed something…
I actually ended up just making the swap and it all just worked.
Even putting the old internal drive in the external enclosure, it sees, and can boot both.