Yes, your b365m DS3H can use a M.2 NVMe SSD.
Yes, your b365m DS3H can use a M.2 NVMe SSD.
The B365M DS3H motherboard from GIGABYTE U.S.A. features a single M.2 slot (Socket 3, M key) supporting various SSD types. This means the board can accommodate any standard M.2 SSD.
These are distinct keying options. All devices use M.2 form factors. The "M" switch connects to the 5-contact port, while the "B" switch connects to the 6-contact port with a large contact. The "M+B" switch links both. SSDs with the M key are uncommon, so comparisons mainly focus on M versus M+B. Most M key drives are full PCIe x4 SSDs, whereas M+B drives may use either PCIe x2 or SATA interfaces. For top performance, the M key drive (small contact followed by a large one) tends to be optimal. Your board includes an M.2 slot that supports both keying methods, allowing compatibility with either M or M+B drives.
The M.2 slot on the motherboard supports both NVMe and SATA devices according to the instructions. Installing a SATA M.2 drive will turn off one of the SATA connections. Note that SATA drives usually use a B&M key, occasionally a B key, whereas NVMe drives typically require an M key, though sometimes they can be B&M keys only, offering just a 2x PCIe interface.