I got arch working on a PocketBeagle described here
https://archlinuxarm.org/forum/viewtopic.php?f=48&t=12623.
Good news is these TI am chips in the beagle family boot in a predictable way from SD card, so all you need to do is set up the card correctly. They have the board type written to eprom, and uboot recognises this. I hope bone blue has been around to make it into the uboot source, as its a bit of a hassle to add. Anyway if recognised it will pull in the correct device tree, and that means most of your hardware will be set up - guess this is needed on the blue as you have so many interfaces.
Now right approach to start from an existing image. That will get you 95% of the way there. Problem is the remaining 5%. Easiest is if you can plug in a uart on the board - had a quick browse this morning, at least one uart is on the pins (uart4?) but not clear to me where the main uart is. Anyway if you can access that it makes it easier to debug problems.
Otherwise the route I chose was to find all problems before you start, develop the solution on another board (I used a BB Black), then only when everything works move to the BB Blue.
Oh yes - check the BB Blue schematic, the UART that will probably have the main messages on is UT0. The pin out you need:
Gnd - 1
(3.3V) - 2
RX - 3
TX - 4
So suggests 3.3V (which is what I'd expect) and only use GND-RX-TX (e.g. don't use 3.3V)