NVMe drives are M.2, they don't look like it - they are.
Anyway, your best bet is the internal adapter. It's not that tedious, seriously, it takes about two minutes..
NVME is not M.2
![](https://qph.fs.quoracdn.net/main-qimg-65e3f3e74f620b9b115bfa2bd30767a8-c)
And M.2 is SATA based, while NVME is PCI-e. Most enclosures especially state that it is not compatible with NVME, while the others just have an outdated description.
Consumer NVMe SSDs use the M.2 form factor.
M.2 carries: SATA, PCIe, USB2, USB3, SMBus, SDIO, UART, .....
M.2 SSDs come in SATA, PCIe AHCI, and PCIe NVMe. Any of which will work in either slot on the board in this machine. Wifi cards are M.2 now, too.