Hi johnny, would you mind elaborating on how you “manually set up boot using systemd-boot” please? I’ve run into an extremely similar issue installing Manjaro KDE on an external SSD connected to a 2018 Mac Mini. When I check the external SSD, the installation seems to be pretty much all there, but of course because no boot loader was installed it’s not possible to boot into it right now.
I can still boot using the thumb drive I created with the Manjaro ISO on it.
If I can’t fix it I’ll create a new post to get help but your solution of manually configuring boot seems to be exactly what I need. I’ve looked at the systemd-boot and bootctl man page but couldn’t really work it out.