The OS from Asus were pretty basic so I was using Armbian. This OS was able to do everything I wanted it to do and was very user friendly.
The ASUS website has improved a lot. They have a list of exciting performance status. Well we already know that the hardware is good. We were just missing a good official operating system and a community of users to develop ideas. Clearly they are trying give a sense that this exists now. More alternative operating systems are on off for dedicated tasks.
It looks like ASUS have taken on some of the existing user groups as their community base. I was aware of tinkerboarding.co.uk some time ago. It looks like they are now the official Tinker Board forum.
Following this are some Youtube tutorials on getting started and a list of requirements. These include a keyboard and a mouse but I tend to run my board headless. So I laugh at your list of requirements.
At the bottom of the page is where we find the downloads. There is a official Android OS but I am focusing on Debian at the moment. The latest at time of writing on this page is dated 17/04/17. That seems quite old. However it you click the SUPPORT button at the time, click the DRIVER & TOOLS tab and then select “other” for the OS. You will find here the latest is version 2.0.5 which is dated 20/03/18 (although the download itself is dated 22/03/18!). That seems much more useful. There is also a list of what has been updated in this version.
I have downloaded it and written it to a 32GB micro SD card. I will plug it into the Tinker Board and let you know how it goes.