Thomann had (still have?) this thing called "stompenberg", where they put up some mechanical switching system so that you could play audio files through the actual pedals in the system, and turn on the knobs / parameters. In the recent years some smaller businesses have started to offer outboard gear in this way. You upload some stem, and can process it through their hardware remotely, and get back the results.
This is cool except that the only ad for this I've come across so far was for analog summing. Remote or not, that concept (going out of one's way to theoretically have something more pleasing than digital summing) always smelled like a scam to me. Like ok, maybe a sample rate a hair above what Shannon/Nyquist demand can't do digital summing with all the right IM distortion of the missing supersonic content or whateve…
They have 60+ rack units with little robot grabbers physically controlling the knobs.
Re analogue summing, yeah it does near nothing in reality. What you're missing though is that what people actually want with analogue summing isn't really technically better sound but technically worse sound. Analogue gear might have a little bit of harmonic distortion, a little bit of crosstalk between channels, certain transformer characteristics etc that theoretically make it sound more glued together or warm etc etc. But ultimately summing is summing and those differences vs. digital are very small (and won't always contribute positively either).