type ACCESS struct {             // ⬇️ ain't no way that this parses
    FIELD_POLICIES		t.Opt[map[string]FPolicies] `koanf:"fieldpolicies"`
}

func (splitter *FPolicies) UnmarshalMapstructure(raw any) error {
    // should be map ⬇️
    slice, ok := raw.([]any)
    // ...
}