Insert / Direct Out from Mixer: TRS Wiring

We are talking about recording live gigs right?
If yes, how do you get mic signals into each 8 channel interface? Do you use some sort of XLR snake “splitter” So your interfaces and the FOH mixer both get the signal, or do you tap into the FOH mixer? If the latter, what’s the use of adding one layer of 3 interfaces instead of tapping a couple of snakes from the FOH Insert points with a modified TRS snake?