Hello lsputman,   The significant fiddling is why field changing of backplane configuration is not typically supported.   We don't have kits and would have to piece part any changes together.   The link Young provided show the two configuration that indicate NVMe support: Figure 15. Figure 16.  
Hello. I have a 2018-era R740xd with the 24-bay SFF backplane (part no. 0P1MJ3).  I can't find any information for that part number, and some of the documentation is confusing. Does that backplane support *any* NVMe drives? If so, how many? If not, can that backplane be replaced with another backplane that supports NVMe drives, or are there other chassis/cabling issues that have to resolved (other than the addition of PCIe expander cards)? If the backplane can be upgraded, can you give the part number for that backplane? Thanks so much S
NVMe Support for R740xd backplane