MagisterCultuum
Great Sage
Founding a religion does not necessarily require researching any technologies. It is also possible to rescue a disciple from a lair, and use that disciple to found its religion. That can happen even in base FfH2, but is a bit more common in my modmod. My modmod allows Priests to be rescued too (which don't have the chance of failing to spread their religion), and increases the odds of it happening when the religion is not yet founded.
Founding religions this way is not exactly common, but it definitely happens. The Ai does not often use its priests to found temples of unfounded religions, but it seems to rush any rescued disciples to a city to spread their faith.
(In my current game I rescued a Savant from a dungeon before I had researched Corruption of Spirit, but another player had already founded the religion the normal way.)
(If any player can found the Empyrean and convert to it before learning Honor, then moving a unit onto the Mirror of Heaven will grant that tech plus a Great Prophet. That advantage is most commonly enjoyed by the Malakim, who can found The Empyrean at Way of the Wise rather than honor and may build Lightbringers with only that tech, but if another player rescues an Ecclesiastic or Vicar and founds the religion then they can exploit this bonus too.)
Founding religions this way is not exactly common, but it definitely happens. The Ai does not often use its priests to found temples of unfounded religions, but it seems to rush any rescued disciples to a city to spread their faith.
(In my current game I rescued a Savant from a dungeon before I had researched Corruption of Spirit, but another player had already founded the religion the normal way.)
(If any player can found the Empyrean and convert to it before learning Honor, then moving a unit onto the Mirror of Heaven will grant that tech plus a Great Prophet. That advantage is most commonly enjoyed by the Malakim, who can found The Empyrean at Way of the Wise rather than honor and may build Lightbringers with only that tech, but if another player rescues an Ecclesiastic or Vicar and founds the religion then they can exploit this bonus too.)