I had a Sandisk Extreme Pro 500Gb PCIe NVME M.2 SSD. I got an USB-C 3.1 Gen 2 Enclosure for it. I have tried it on 3 different 2017 and 2018 macbook pros and an iMac. The Max read/write speed that I can get is 40MBps. I thought the problem might be with the enclosure so I tried 4 different enclosures and still same result. I installed the SSD through PCIe to a desktop and read/write speed were astonishingly high.
I got a Samsung T5 External SSD and even with one I have the same problem. I have seen many reviews of T5 on youtube with Mac which all were satisfied. Am I missing something? Do I need some sort of Driver for it? I’m running a 2018 Macbook Pro with MacOS Mojave