Vitamin D is often treated generically, sometimes even not specifying the index. According to this article, there are five Ds (D1, D2, D3, D4 & D5) and only D2 (ergocalciferol) and D3 (cholecalciferol) can be used by our bodies.
This article goes further and makes a difference between D2 and D3. D3 is clear winner (my emphasis):
The majority of ...
From what I can gather, there does not seem to be vegan food sources that provide vitamin D3. From This source, they first provide a table with the recommended daily intake of vitamin D:
Since the US government still doesn’t count the value of D2 and D3 as
being different, they only report an RDA for the umbrella category of