I am not one of the team and simply commenting from my own research and experience in this. Theoretically you can probably compile for any cortex board, there will probably be modifications needed though from board to board.
The main limitation when switching boards will be audio i/o, the Elk Hat is a very cool bit of kit and from my research which I have been doing for over a year getting multiple audio ins and outs working on the PI and most other boards requires a fair bit of engineering due to the general lack of I2S pins on common SBC’s. I think the only board that can handle multiple ins and outs without some sort of TDM multiplexing at this time is the Beagle, however it is quite under powered compared to the Pi.
The ELK Hat looks like it has an FPGA onboard to efficiently handle TDM (Basically squeezing multiple channels of audio down one I2S bus)
I am sure more hardware will start appearing pretty quickly now that the seal is broken so to speak.
Just my 2 cents.