HP Split X2 (13-r010dx): Tablet Innards
I took apart this convertible tablet/laptop with the goal of upgrading a SATA hybrid drive to a full SSD, but I was foiled. Since I had it open anyway, I took a look around. With the hybrid drive sitting directly in the middle and batteries on either side, circuit boards were necessarily scattered on either side with ribbon cables connecting them.
Most of the computing brains resided on a circuit board up top, and peripheral interfaces lived on the bottom. Including the microSD slot, headphone jack, charging port, and the docking connector. In between them were black speaker assemblies, one left and one right.

There were also provisions for interface cards to flank left and right of the main processing board. On one side is a WiFi interface module, with wires leading to antennae. The antenna is smaller than I had expected, but I don't know enough to say if this necessarily meant reduced WiFi range. I also noticed the WiFi module didn't occupy the entire width of the interface slot, leaving a few pins unconnected. I don't think I've ever seen that before.

The opposite side is even more interesting, with pads for an absent connector. This has roughly the pin counts to be a M.2 "B key" edge connector which could support a M.2 SSD. There's also a hole cast into the chassis that's roughly the correct distance to secure a M.2 2280 card. But like my previous experience with unpopulated connectors, several adjacent supporting components also seem to be missing from the circuit board so I am not confident I can just solder a M.2 connector and make things go.
I was curious if the 4GB RAM on this board could be upgraded. If a standard memory module is here it would be under the metal shield covering most of the processing board, but I didn't want to dig that deep just yet. 4GB is enough to cover basic tasks and it is clearly not designed to be easily upgraded.
[UPDATE: I dug deeper and didn't find memory modules.]
With curiosity about the tablet internals satisfied for the moment, I reassembled the tablet module and turned my attention to the docking base.