In our project, some SMEs (non partners) will obtain services from the project partners in the framework of pilot implementations. Those beneficiaries will be selected following an open call under pre-defined criteria. Those services have a maximum budget of 8400EUR (VAT included). How should we answer the question II.2 in the state aid section in JEMS? If the answer is YES, is GBER Article 20a the relevant scheme?

The answer is yes, and it would be recommended to detail all the activities related to this specific work plan context. It would be also suggested to add the selection criteria you will consider for your open call.
These latter should be less restrictive as possible to ensure a broad participation by potential candidates.