Mods' advancements upon joining the world being printed to chat can be fun but also overwhelming in big modpacks. I'm aware the advancement file can be edited, but a proper config option would be preferable!

Probably just adding the rule /gamerule announceAdvancements false，or edit the assets\mod_lavacow\advancements\mod_lavacow\root.json directly, as it's quite complicate to config json files.