I’ll share my setup/approach which is ever-changing as I’m always learning ways to improve, but anyway
Step one is figuring out the space-
I have a fairly well-isolated studio as far as external noise, and a pretty dead room with lots of absorption as far as internal. I have sort of a poor-man’s live-end-dead-end thing going on acoustically and the piano is in the “live” section (which is still fairly dead as it’s a low-ceiling bedroom). I had some leftover absorption material when I was setting up the space, and the piano was feeling a bit muddy since it sits in a corner, so I wrapped a bunch of absorption material up in fabric and it lives on top of the piano essentially as a big bass trap.
The front cover hasn’t been on my upright in years- I always keep the strings exposed since I’m always playing with them, and it sounds better to record it with the cover off since it adds some clarity, much-needed volume when doing felted stuff, and you get all those fun mechanical noises.
As far as mics go, I’m not a wealthy man so atm I use Oktava 012’s, typically with the omni capsules though I have used the cardioid capsules from time to time if things are getting too messy with the room sound. Mic placement varies per track based on what register I’m playing in, if I’m single-felting or double-felting, how loud I’m playing, the dynamic range of the piece, etc.
Always an AB setup, and to find the right placement both left-right and front-back (relative to the piano) I’ll record a bunch of different placements, write them down, then pick which one I like best. Typically the mics are 10-18’’ apart from each other, and anywhere from ~10-24’’ away from the strings. I’ve found more often than not with my setup, the best sound a lot of the time is having the mics parallel with where my head is, but again this could be wildly different for you depending on all these variables. As far as placing the PAIR left-right, I usually dictate that by what register I’m playing in and set up the mics on the left and right bounds of that (it’s rare that I’m playing way up and down the keyboard).
Because these mics/my room aren’t the best though, I typically process the shit out of things and have to spend a lot of time EQ’ing, often pretty heavy-handed, to get things sounding clearer. This is often a lot of surgical subtractive EQ in the low-mids, and some boost in the highs to bring out the mechanical sounds. And if going for that intimate felty sound, obviously compression is a must, but I have no set-rule for how I do that as it can change a lot based on the track, just use your ear 
the only constant is cranking the makeup gain a bit since the compression is typically pretty heavy and the source sound is fairly quiet to begin with. I use Fabfilter plugins (for basically everything) but you could achieve the same effect with whatever.
