My best friend passed away recently. He was single, childless and under guardianship. Supervision was exercised by a legal representative for the protection of individuals. Can the guardian seize a notary to take care of his estate?

Yes. In the event of the death of an adult who is the subject of a protective measure exercised by a legal representative for the protection of adults, the latter may, in the absence of known heirs, seize the notary of the deceased through a view of settling the estate or, failing that, ask the president of the departmental chamber of notaries to appoint one (article 1215 of the Code of Civil Procedure).