[Android Q&A, Help & Troubleshooting] dwkindig:
Uit232b-u03

Thought I'd chime in; I have one of these wallboards, model # UIT232B-U03, nominally equipped with an RK3188. Here's what I've found:

Misc. Device Info

RIL Ver: KitKat ril-rk29-dataonly v3.3.00

Build No.: Z05-outform-32-B4.21-20160324

Build Fingerprint: rockchip/rk3188/rk3188:4.4.4/KTU8Q/eng.root.20151208.162319.eng/test-keys

Board / Chipset: rk30sdk / RK30board

As you might notice from the Build Fingerprint, this model appears to be running an engineering build of Outcome/ContextMedia's KitKat ROM; this screen was pulled from a working clinic, but USB debugging was already enabled and connecting via adb shell automatically dumps you into a root shell. There's nothing more you need to do to gain that access.

The device info (courtesy of Droid Info) references three different RK chips in a few places: RIL Ver. (rk29); board & chipset (rk30); and everywhere else (rk3188, specifically). I don't know what to make of that. Maybe something to do with it being an engineer build? Could be an engineering sample board, too -- I need to check for that info.

Personalization

As mentioned, it looks like this unit (and maybe other UIT2xx-xxx revisions) appears to come pre-rooted with USB debugging already enabled. There's no need to authorize any given machine on the tablet when connecting over ADB for the first time, either. If you still want/need to access the system settings, three-finger-tap on the application logo in the bottom-right of the screen (tapping multiple times will just cause a credits list to pop up). The password to leave the application for the Android system settings is cat10dog, as has been noted elsewhere.

Before I loaded anything new, I went ahead and factory reset it to see what it looked like. Upon doing so, the only system application was Zygote -- it looks like it's a modified version which is serving as the "launcher" for this tablet, and which forcibly reloads the application whenever it is closed for whatever reason. From factory reset, it will launch into a first-time setup screen, where it looks like you can configure the application and get connected to wifi/ethernet and download the remaining system apps (this is my impression; I didn't go through with it, but I imagine the application will want to verify a license or something). Uninstalling the modified Zygote seems to not kill the first-time setup screen (makes sense -- it's meant to stay resident and likely has everything it needs loaded into RAM at the time), but you can install Nova Launcher 5.3 (last version to support KitKat 4.4.4) and then Zygote fully disappears and you won't get bothered about setup anymore. (I have no idea what happens if you remove Zygote and then don't install a launcher. You can probably still connect over ADB, but I've never seen a launcher-less Android.) Other apps can be installed at this time, too.

As noted elsewhere, the Home and Recents soft buttons still do not work. I'm not 100% sure, but I think that's something stuffed in the ROM itself and may not be configurable (maybe through the commandline?). But, you can just use the Back button to go back to the home page at any point.

I have not had any success installing TWRP: It turns out, despite the chip being labeled in all ways as an RK3188, it is in fact a lower-specced RK3188T (1.4Ghz top speed). Every version of TWRP for the RK3188 I've tried has resulted either in a bootloop (unplug from power and plug back in to return to system), or a black screen, or the TWRP splash screen but which never progresses beyond that step. (This reminds me, I need to check on the black screen instances to see if the recovery executable is running at all, and what happens when I try to manually start it.)

On the off-chance anyone has a TWRP build for the RK3188T for me to try, I'd definitely appreciate it! :D Or indeed any ARMv7-based build, if I'm just going to be blindly loading recoveries to see what happens. (If anyone has any advice for debugging the recovery loading process, I'm rather a noob at this and could use any information about where to look for logging info, or to make it output a log at all if it doesn't by default.)

OH, and uh... if anyone has a stock version of the recovery partition, could you send it to me? I didn't back it up before writing over it... :(

Other than not getting to install TWRP and get all experimental with ROMs, it is usable in its current state as an old-but-servicable, pre-rooted-for-your-convenience-no-supersu-required, massive Android tablet. Too bad Pocket Camp requires Android 5 since a few builds ago...

Edits for grammar, spelling, extra info.