As for your problems installing it on other boards, where are the drivers for them? Your classic desktop installation comes with drivers for almost every laptop/desktop board. Android doesn't because the vendors don't contribute. A snapdragon SoC requires a binary blob from Qualcomm. There is nothing you can do without it. It has nothing to do with AOSP being opensource or Google controlling it (Google controls other aspects, AKA the Play Services).
Trying to get the xda builds and LinageOS working properly is subjectively speak—difficult and heavily device dependent.
I’m not sure about x86 images, but arm are heavily device dependent.
Would love be proved wrong. I’m looking for android images actively.
In order for device manufacturers to get the Play Store on their phone, they have to give in to Google's demands to add the Google search box on the home screen of the phones.
Apart from this, Qualcomm doesn't release open source drivers for GPUs etc, making it even harder to use pure AOSP on flagship devices.
What's wrong with this? The Play Store is subsidized by search revenue, it makes sense to tie them together.
There's a bunch of SBC manufacturers (pine64, odroid, orangepi, etc) worldwide that have managed to compile AOSP for questionable hardware. However, it is noteworthy that almost none have been able to compile images for Android 7.1 and above that work without hiccups.
Android being an open source OS is nowhere near as easy to install as a regular linux open source OS.
I've been trying to get my own android / androidTV box working on popular hardware like rPi and other Amlogic, Allwinner, Mali based boards without much success. Even devices manufacturers have troubles with the same (talking about SBCs here).
Android is open source only for name sake. Google's deliberate control over the entire Android ecosystem is undeniable.