I created this problem over on the github issues page but for some reason they deem it a support request rather than reporting a bug so they told me to post here.
The TLDR is basically you cannot execute any queries - and thus dashboards either - in the new V9 UI without the site breaking. I have inspected the dev console on the browser and the issues are all react issues.
Rather than repost all of the detail I added already, please see my thread over on github for my detailed description explanation / screen shots - Github issue page
Thanks for your help and work on this project.