When you disable some vanilla materials but not used in trim in vanilla minecraft(like coal), these advancements are still there(unachievable). Maybe these advancements can be disabled automatically(if players do not have all the trim mod)? Or will there be a master control for advancements?

Maybe these advancements can be disabled automatically

Likely what I will do

split this mod into vanilla, vanilla-like and all-the-trim version

Not gonna happen, I already maintain enough projects + a job + uni

Or maybe we can split this mod into vanilla, vanilla-like and all-the-trim version? I think these would be nice for players who don't want to override minecraft too much.

Will deleting advancements json files in mod/data/bettertrims/advancements be safe? Like disabling advancements manually.

Yes