I’ve used M31 once, a few months ago, in a 1046 Belgian pale. There were two different colours of grains, so a blend of two yeasts or a yeast and something else? Enzyme or nutrient?
The beer was pretty good, and I had a surprising moment when I discovered Du Pont on keg in a local bar here in England, and on tasting it immediately thought how similar it was to the M31 beer back at home. Not the same, of course, and not drunk side by side, but ball park and close enough to trigger that thought.