I have an unusual device - an "ITX-3588J" board from the Chinese manufacturer Firefly (T-Chip Intelligent Technology Co.) using a Rockchip RK3588 ARM SoC - and it comes pre-loaded with Android 12. This Android is very, very minimal: it has virtually none of the apps that one would expect on a phone or tablet, but also has readily available root access and everything unlocked. My aim is to use it to run a virtualized Ubuntu Linux workspace (or at least whatever something like "Linux Deploy" does) to have the ability to make use of both Android and Linux apps on the same machine. While this vendor also offers an Ubuntu 20.04 native image, it pretty much is mutually exclusive with Android because each has to flash to the integrated eMMC.
Yet to install any further apps (including, ideally, a better web browser, too), I need Google Play, and that's not there. And my question is, how do you install it the "right" way, given it's the "app that installs other apps"? I have found very little entirely relevant material describing how to do this. I once managed to get it almost to go with .APK downloads from apkmirror.com, but do not remember how I did that now, and subsequent readings have made me wonder if that's not really the right way to do this. All other material I've found talks about installing on an Android emulator a la Android Studio, but is useless because they always (for that application, reasonably) just point to the appropriate AS tools, which obviously won't work here, and I basically blundered my way though that one time. There obviously has to be a way to do this because presumably it's what Android OEMs would do in the factory, but I also have no idea where that is documented.
So my question is: how do you install Google Play on a virgin Android system loaded to real hardware - including Google Play Services and the Google Services Framework - the "right" way?