Luke 8:35 uses the same phrase 'sitting at the feet of Jesus' for the healed demoniac — who was clearly not being trained as a rabbi

Luke 8:35: the demon-possessed man, after being healed, is found 'sitting at the feet of Jesus.' He was with Jesus for only a brief time before being sent back to his town. Luke is comfortable using the phrase for someone who is not undergoing rabbinical training — just someone who is learning from Jesus.