It can be helpful to automate the level of the ambient, audience/rear-facing facing microphone(s), either manually with envelopes or automatically "soft-ducked" with side-chaining keyed off the mix of soundboard elements, or the forward/PA focused mic channels. Bring it up in between songs and in quiet sections and down as the music get thicker and/or the audience goes distractedly chatty. Just be careful to avoid obvious perceptible level changes. Compression can do that somewhat, but can bring up the chatter.