Not sure if this is a Linux hot-plug problem but if I start my NUC5i5RYH without the external SATA hard-drive going, I can not later turn it on and it be auto detected. I have the start the NUC with the SATA device going for the bios to maintain the presence of the SATA interface off the M2 connector.
If possible please put in the bios an option to always enable SATA if the User so chooses.
I understand why this is the way it is; the expectation is that the M.2 interface, if used, is always used. Still, these adapters that exist the SATA lane do exist and folks may want to make use of them. I have passed this request along to the NUC development team...