I went ahead and did it, so I'll describe the answer for anyone who may have the same question (simple instructions on how to add a 2.5 inch SSD will be included at the very bottom):Simply put... yes it's possible to add a third internal drive to the G5 5000. In total, there is one M.2 slot, one 3.5 inch SATA slot, and two 2.5 inch SATA slots. My desktop came with an M.2 SSD and a 3.5 inch HDD included as mentioned, so for me there are two vacant 2.5 inch slots available.To use a 2.5 inch SATA slot, you would need an internal 2.5 inch SATA HDD or an internal 2.5 inch SATA SSD, which themselves require a power cable connection and a data cable connection to the motherboard. The desktop already comes with a SATA power splitter cable that can power all three SATA drives to the one SATA power port on the motherboard. But there are no extra SATA data cables available, and the included data cable that connects the included 3.5 inch HDD to the motherboard is too short to connect a 2.5 inch drive to the motherboard. And it's not going to come included with the SSD. So if you want to make use of the 2.5 inch SATA slot, you would also need to buy a separate SATA data cable (18 inch, right-headed, is optimal) if you don't have one already lying at home.The SSD doesn't require screws as there are 2.5 inch trays included in the desktop to comfortably house the drive in. Just take one of the trays out and insert the SSD into the tray, and then put the tray back in the 2.5 inch slot. Plug the SATA data cable into the SSD and into a vacant SATA data port on the motherboard (there are three such ports in total, clearly labelled). Plug the included SATA power cable to the SSD and that's about it. Watch a Youtube video on how to set up the SSD on the computer but it should be simple. Don't bother with the Dell manual... it doesn't mention about how to use the 2.5 inch slots. But even though this was my first time inserting a new SSD on a computer, it's a fairly easy process.Simplified instructions:1. If you don't have one lying at home, buy a SATA III data cable that's at least 18 inches long. 2. Open the left side cover of desktop and take out a tray from a 2.5 inch slot.3. Put the SSD in the tray and insert the tray back into the slot.4. Insert the SATA data cable into SSD and port on the motherboard.5. Insert the included SATA power cable into SSD.
Hi, I bought a G5 5000 desktop that came with a 256GB M.2 NVME SSD and a 1TB 3.5 inch HDD. I saw that there are two 2.5 inch slots with some vacant cables. I was thinking of buying a 2.5 inch SSD for more storage, specifically the 500GB Samsung 860 EVO. I just wanted to make sure if there would be any problems getting it to work on my desktop (It's a 500 W desktop on a 1650 Super, so I think power supply won't be a problem). I never installed an internal storage drive before so I don't know if I have to buy anything else. I heard that installation involves two cables, a tray, and some screws. 
Dell G5 5000 adding a 2.5 inch SSD