In 1.20 the animal dictionary seems to crash the game when I turn the page, un sure if this is due to the mod pack (slightly flavored) or the mod it's self

I'm having the exact same problem. I'm using my own modpack. here's my report: https://hastebin.com/share/mehakaqole.yaml

I have the same problem too. Heres mine:
crash-2023-10-08_09.26.30-client.txt

There is an error with the Jellyfishes model. If you are having this issue the game will crash whenever it tries to load the model, meaning if they spawn in your game, the world will keep crashing. I suggest for the time being that you go to the config and turn off the jellyfishes spawns so that this doesn't happen. It does not solve the issue with the book, but it keeps your world playable.

Stop using Optifine

There is a way to keep using the dictionary w/0 crashing?

Stop using Optifine

Not helpful at all. The rubidium port currently doesn't work with the latest update.

dupe #1900