I have just discovered the alternate RTOS, RT-Thread and decided to move on to it.
It has good support for the RISC-V chips, and mainly for the cheap chips/boards that can be purchased through outlets such as Aliexpress. I'm a big fan of these cheap low cost dev boards.
RT-Thread is now estimated to be the 3rd most contributed rtos!
This book will stale as in it's current state, and I have no plans to progress. But fortunately it cover's the most basic chapters, good for a beginner.