My goal is to get OMV5 running on my RockPro64 (previously running OMV4 on an Ayufan image).

I'm using this guide here from over on the OMV forum which suggests that Buster Server is the only thing that will work; this is based on the 4.4 kernel, and the suggested alternate of Buster Minimal is not present.

I've tried downloaded from multiple locations and cannot get the SHA to match.

The 256 per Checksum utility is 760BD8FA51316D07E875D5B8687E837C8C00070E68F44B8B413C76EC217C606B

while the file from the Armbian download site is 3ddc7bc3e47bc39a9a9bed6109d35ca712bd34a6206121d37814ca8faf4b8798

If i try to flash the image to SD and boot device fails to boot (performed all required tests and tried different cards).

So at this point I don't know if i'm looking at a bad download or a compatibility issue with Buster? Any help would be greatly appreciated!

We changed compression from 7z to xz - perhaps that is confusing you? https://docs.armbian.com/User-Guide_Getting-Started/#how-to-check-download-integrity

 

Perhaps you are running into this problem - some Rockpro64 boards has issues with modern kernel.
 

It has nothing to do with Buster , Stretch, Ubuntu ... its lower level issues, perhaps quality issue.

Since you didn't tell exactly which image (provide URL) did you try, I can't help you more then this.