Hello Wang,
The EN15804 add on is rather to reflect requirements from the EN15804 norm, which is of course for EPDs in the construction sector, but it contains datasets for many different sectors. Other products have different rules, especially for other products, the somewhat special inventory-based indicators of EN15804 are not needed typically (material for recycling, exported energy, etc.), and thus also a special database is not needed. Which means that a "normal" ecoinvent license for example is sufficient for an EPD. I have verified for example an EPD for a tramway that was using the normal ecoinvent database.
Hope this helps, best wishes,
Andreas