RE: 32GB in Inspiron 13 5000 series (5378)???
Well, I'd like to confirm that I installed 32GB (2x16GB) of DDR4 in my newly arrived Inspiron 13 2-in-1 5378, and it was recognized without a hitch by the BIOS. I've only spent a few hours using the system getting Win 10 configured and set up, but it works perfectly fine with the 32GB. So like other observations that have been made, Dell might not have actually certified the use of 32GB in this particular system, but it seems to work without a problem.
For those interested in the specific details of DDR4 I used, here is the link:
Another note--I was expecting to find an available M.2 slot in inside for an eventual upgrade to an M.2 SSD, but there is not one. The only M.2 slot I saw is filled with the wireless card. This is pretty darn frustrating as I was planning to upgrade to an M.2 SSD in a few months. I've subsequently done some searching on these forums, and see notes to the effect that only 7000 series machines have a second M.2 slot. But that is not what the User Manual says!!! If you can't even count on the dedicated user manual for correct specs this is pretty frustrating. And it's a little bit infuriating because Dell probably saved a whole $0.49 in fabrication costs by eliminating this second slot. I think I will eventually write them about this because it is a big disappointment.