Trying to install Manjaro on my iMac, I booted it into target disk mode, essentially making the iMac act as a hard drive. After connecting it to another computer with a thunderbolt cable as required, and booting into the live environment, the installer failed to detect the presence of the iMac. Adding support for hard drives on the thunderbolt port(s) would fix this issue.
Hi and welcome,
Never seen this done or tried it. Seems like a interesting project Support for thunderbolt is in the kernel, so this might be an issue with the detection, arch wiki states: Modern Thunderbolt devices implement security modes that require user authorization when connecting devices
Further reading: Thunderbolt - ArchWiki
Maybe add some more info about the hardware detection. Terminal output from the livecd
should provide enough initial detail for users to get a good idea what is happening on your side.