This is a duplicate post to the links below, but creating a new one to see if Dell can respond and help address.

• https://www.dell.com/community/General/Inspiron-7000-Gaming-7577-Problem-adding-2nd-hard-drive/m-p/5183723
• https://www.dell.com/community/General/Dell-Inspiron-7577-2-5-inch-SSD-cannot-be-detected/m-p/5169157/highlight/true#M934100

I was hoping after the 1.4.2 BIOS update on Feb 18th 2018 that adding a SSD would be supported.  It unfortunately is still not detected by BIOS or Windows.  Using a mechanical drive works without issue.