How to set RMS on recorded chapters

You can use RMS Normalize. It has to be installed.

https://forum.audacityteam.org/t/rms-normalize/45334/1

But.

Are you planning on submitting to ACX/Audible? Did you post a test to see if everything was OK before you read the whole book? Or is that message from ACX?

Audacity has an Audiobook Mastering suite of tools that guarantee Peak and RMS and if you read well in a quiet, echo-free room, Noise should fall in and that’s all you need.

I need to change machines.

Koz