The Optimus A80 is not officially supported by Allwinner for Linux-sunxi; however there are some community members which occasionally update the drivers for audio, network etc (this link may be useful - http://linux-sunxi.org/A80#Sunxi_Community). Also you are correct in saying that the Optimus supports Android only up to KitKat (4.4).
In regards to your question about driver similarity between Android and Linux, they are indeed very similar in terms of core functionality, of course there are some differences with regards to interface and memory management.
If you are after the latest possible device with the latest drivers, that is also available on the market right now then the Asus Zenpad would be your best bet.
However I wouldn’t worry too much about the age of the devices, the drivers available on the Optimus A80 and Nexus Player will be pretty robust and if you do find any bugs with any platform with PowerVR you can let us know through the forum or drop us a ticket in the support portal (https://pvrsupport.imgtec.com/), we will try to replicate the problem and verify if the issue still exists in the latest version of our drivers.
We greatly appreciate any feedback you can give us, hope this helps.