I've been playing for 19 hours on my save and I still can't get this quest to start. Been running around all over the Commonwealth doing quests for settlements because I thought Preston was supposed to tell me about it after I've done so many.

What is happening here?

What level are you? Maybe it is limited to it?

Would ask about your status on MQ as well, but I never got to Diamond City and I still got this quest.

Hmm... what is the state of your settlements? Since Minutemen are all abut this feature, maybe they need to be big or happy enough?

I certainly have enough, like over a dozen active though I've ignored them all since I just want to start this quest.

Main quest point is just after the BoS arriving.

I've also done the Sanctuary quest for the Minutemen.

This is about the settlements I presume? If so, try to make several of them happy and properly defended, aka make sure they don't have warning signs.

That could be a good shout. Good idea dawg