(update 2022-03-04 12:24: Added links to other documents. No change to Radio Operator Handbook)
The Radio Operator Handbook version 3 is available here:
https://drive.google.com/file/d/1npevX8Yuyc8K0xZjC6woTAh1FletAd4I/view?usp=sharing
Version 3 is the first version that has been released.