Pretty sure I'd explained this to him last night but I guess not. The drives he has are NOT flashed and will never ever work with 4K UHD blu rays unless he gets them flashed.
There are no workarounds, another Mac is not going to change this behavior.
Compatible MAC UHD Drives
Re: Compatible MAC UHD Drives
The Original "UHD Friendly" Drive Seller
https://www.makemkv.com/forum/viewtopic ... 20&t=17829
https://www.makemkv.com/forum/viewtopic ... 20&t=17829