Mods:
Ars Nouveau version 4.12.4-all
Curios API version 5.10.0
Dynamic Trees version 1.3.3
Dynamic Trees - Ars Nouveau version 1.2.0
Patchouli version 1.84

Issue:
When launching the game, I get this error:

• Failed to load book dtarsnouveau:guide defined by mod dtarsnouveau, skipping
  java.lang.IllegalArgumentException: Book dtarsnouveau:guide has use_resource_pack set to false. This behaviour was removed in 1.20. The book author should enable this flag and move all book contents clientside to /assets/, leaving the book.json in /data/. See https://vazkiimods.github.io/Patchouli/docs/upgrading/upgrade-guide-120 for details.

This should just be a simple oversight and not too difficult to fix.