Right now the Inhumans overlap with either the X-men or the Eternals. So I could see them being benched unless they find an angle. I just choose the space opera angle from Annihilation. That's where the Inhumans were space bound and they served the Kree. Crystal married Ronan in a political marriage etc.
I think just having Thor or Captain Marvel stumble upon Attilan in their space travels would be fine. The Guardians also work and the plot is just a Doctor Who episode. Ya know, travellers stumble onto a new place and get involved in local problems, eventually helping the natives deal with it. You could do fun matchups and turn them into subplots etc.
Thor v Inhumans writes itself .