What is the ruling on the performing congregational prayer outside the mosque while there is more space inside the mosque
Congregations may gather at any site for the purpose of prayer. The mosque is supposed to serve the needs of the Muslim worshipers as a comfortable and accommodating site. However, if people do not realize that there is more space inside the mosque and pray outside then there is no harm in that and should not cause disagreements. In fact, those who wish to pray inside may do so just as well as those who wish to pray outside, without a rift.
I hope this helps.
God knows best.