5040MT motherboard M.2 slot supports sata ssd.  Spec includes    The M.2 slots supports nvme ssd too.If you use the stock psu which is 240w, best gpu is probably gtx 1650 (you need to skip mechanical hdd/dvd to save power).  If you upgrade to 360w Dell psu, you can run gtx 1070/1080 or rtx 2060/2070.
Does Dell Optiplex 5040 MT support M.2 Sata SSD? and whats the best gpu it can run
Does Dell Optiplex 5040 MT support M.2 Sata SSD? Whats the best GPU can It run 
also?