Advancements is one of the original requirement types supported in Skillable (Original Mod) and has now been improved in the code to be more reliable for gating. The Advancement Syntax is as follows:

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Example:
adv|ResourceLocation

Working Example:
adv|minecraft:husbandry/plant_seed

This works for any and all Advancements even those added by other mods than minecraft, however the correct Resource Location needs to be specified.