This is a financial disclosure requirement.
Support refers to financial support given by EU countries (Members States) to producers of renewable energy.
This covers European Member States direct support to the production of renewable energy.
This is mostly relevant for electricity production within the EU.
If you have received direct financial support by an EU member state to produce renewable energy covered by EU RED II certification, you should disclose it here.

‘Support scheme’ means any instrument, scheme or mechanism applied by a Member State, or a group of Member States, that promotes the use of energy from renewable sources by reducing the cost of that energy, increasing the price at which it can be sold, or increasing, by means of a renewable energy obligation or otherwise, the volume of such energy purchased, including but not restricted to, investment aid, tax exemptions or reductions, tax refunds, renewable energy obligation support schemes including those using green certificates, and direct price support schemes including feed-in tariffs and sliding or fixed premium payments.