Thanks for the great response and the details.
My primary goal of running a linux OS is to run PFSense and portainer so I can run some of the tools I want to like PiHole among other things. The reason I want Ubuntu is it was the selling point SeedStudio used to cause me to buy it and their documentation is sadly lacking right now.
So setting up Ubuntu isn’t the issue it’s getting it running on the LinkStar that is an unknown to me and like you mentioned I don’t want to brick my new toy. On my Pi I’m using the RPi memory card imager so you click click click and you have a working/usable Pi. For the LinkStar Google has no useful links for this install specifically (just points back to SeedStudio which says “coming soon”).
I’ll take a look at the guide for the Pi you linked to and try it out when I get back home from a trip next week.