I grabbed the latest ISO that is 3.9, following the links in the documentation. Troubleshooting a CentOS error during the boot-to-install media that my new hardware (Intel family 6 model 122) is not yet supported, I found that actually v4 is the better platform, but checking again, the code is available but not an ISO that I can boot from. If that is not available (maybe I’m looking in the wrong place) and not a priority (meaning not going to happen soon), then I can do a base OS install and use the instructions to step through it.
Aside from that, I am delighted to find the Raspberry Pi 4 is a possibility - I purchased an Intel-based small NUC-like computer because I misunderstood the hardware requirements. As a separate effort from the ISO boot install, I might try out the Pi option. As a newcomer, I haven’t actually used Rockstor yet, but thanks for everyone’s effort because at face-value, this looks like a great contribution to the community. Rock on!