You’re stuck with Win10/11 on this one. Can’t find much on installing Linux, ChromeOS, or FreeBSD on this. Yeah, I know this is a Windows DevKit.
It is also very-very slow.
Popping extra $10-15 into bigger SSD may speed up things considerably. But for hardware along this deal seems pretty good
Can the memory at least be upgraded? The boot drive is likely on board only.
Not upgradable 
. But by looking into forum some people got lucky by receiving 8gb ram vs advertised 4. That’s a big difference.
Hmm, worth it or not?
No. Unless you want a dev kit for Windows ARM that is too slow to be a dev kit for windows arm.
Tried to find info on the HDMI to see if 4k was possible for sick curiosity and I could not find that information which does not look good.
I guess if you have a use case for it but I don’t think many people can think of one which is why it sits at this price
(As reference I am a software engineer, never for windows arm, so take that with all the salt you like)
I read somewhere the hdmi outputs 2k. No, just a cheapie desktop would be my purpose.