Who was in the wilderness assembly with the angel at Mount Sinai?

Stephen identifies Jesus of Nazareth as the one who was in the called-out assembly of Israel in the wilderness with the angel at Mount Sinai, along with the fathers. The angel spoke with Him there, and He received the living oracles, the Law.

Les explains that the 'church' in the wilderness is the Ecclesia, a called-out assembly of the children of Israel, not a church organization. He notes that when God called Israel out of Egypt, they became a church without any church organization. Stephen, trying to prove Jesus was the Christ, refers to Moses' prophecy of a prophet like unto him, then identifies Jesus as the one who was in that wilderness assembly with the angel at Mount Sinai, along with the fathers, and who received the living oracles, the Law.

Acts 7:38

This is he, that was in the church in the wilderness with the angel which spake to him in the mount Sina, and with our fathers: who received the lively oracles to give unto us:

Who was in the church in the wilderness with the angel at Mount Sinai according to Acts 7:38?

According to Acts 7:38, Stephen identifies Jesus of Nazareth as the one who was in the church in the wilderness with the angel at Mount Sinai. That church was the called-out assembly of Israel, and He received the living oracles, the Law.