Updated: May 29
Q: Is it permissible to prayer with an Imam through a live broadcast like Facebook Live or Youtube?
A: No. If both you and the Imam are in the masjid, following is categorically valid if the Imām’s movements are known. If you are not gathered inside together, but are out on the courtyard or street, it is stipulated that the Imām, or those behind him, are seen, even if just during a part of the prayer.
Source: Bidayat al-Abid