There is a much smaller community of individuals actively managing colonies of solitary bees in Michigan. There is a small group of cherry growers who use horned-faced bees (Osmia cornifrons) for supplemental pollination of cherries in the Traverse City area and I know that there is a small colony of O. cornifrons at the Northwest Michigan Horticultural Research Center (https://www.canr.msu.edu/nwmihort/index) in Leelanau County. I am sure that scattered about the state, there are others keeping solitary bees, but it is certainly not as widespread a practice as honey beekeeping. I unfortunately do not have any forums or groups that I could recommend to you. Dr. Rufus Isaacs is engaged in a great deal of on-farm pollinator research involving native Michigan pollinators and he would probably be your best source of information about such groups if they do exist. His contact information can be found here: https://www.canr.msu.edu/people/rufus_isaacs
There is also an MSU Extension Consumer Horticulture instructor, who teaches residents about solitary bees and how to manage backyard bee hotels. His contact info can be found here: https://www.canr.msu.edu/people/nathaniel_walton