I am looking for explicit mention in KMG Mahabharata that Karna learnt vedas from Drona (will be helpful if there are passages that show he conducted vedic rites). I don't think he learnt vedas from Parshurama but I might be mistaken.

The reason being Manusmriti and other dharma shastras seem to indicate that children born out of Pratiloma marriages (e.g. Suta) are not eligible to learn vedas. So any reference will be helpful .