@linux-aarhus I understand how BIOS/MBR and EFI/GPT work (in theory), but all my installs (in the span of the last 10 years) used MBR with GRUB. I never had issues with them. I even experimenting removing the boot loader on purpose, then put it back. Never had issues.
Now I have installed Manjaro the way you described (without the encryption and I used XFCE instead of LXDE). But, still, on the HP laptop it doesn’t see it. However, besides the Asus laptop, now it boots even from a non UEFI machines (I tried it on another old laptop that supports only MBR, that previously didn’t boot from the USB SSD).
So, I guess, the problem is the laptop, somehow… but I wonder: why/how does the Live Manjaro stick work?! Could you explain how it’s made bootable?