I believe the very first masses were held in living rooms, porches, yards and even stables. I believe that’s where Prisca and Aquila held there services. “Aquila and Prisca greet you heartily in the Lord, with the church that is in their house.” 1Cor 16:19 This is one where you can truly say, “if it was good enough for the Apostle Paul it’s good enough for me”
In the East, the first converts were Jews and their synagogues became the place of worship. To this day, the Maronite Catholic Church retains certain architectural synagogue elements in their church designs, like the bema where the Gospel is proclaimed. In the West where Aquila and Prisca lived, christianity was outlawed so it was practiced underground .. literally ... in the catacombs.
In times of persecution, christians must resort to whatever means are available. In the Ukraine, during the communist regime, christians hid sacramentals in their homes. When a priest was able to visit, he was sequestered in a hidden room. Word spread carefully to others in the village who would randomly "stop by" the house. Under cover of darkness, curtains would be drawn, a table set up as an altar, sacramentals retrieved from their hiding places and a mass celebrated. They worshipped at their own risk. Hardly comparable to someone celebrating mass on the picnic table in peace time.