Legal Question in Family Law in Montana

If bio dad is hiding on the reservation, I assume the child is at least some blood quantum Native American. If that's the case, welcome to the more complicated world of Indian Child Welfare Act. Step-dad will need to comply with ICWA. I've done only a few adoptions that fell under ICWA, and they were more than five years ago, so I will not venture into this territory and make mistakes at your expense.

About service of process: The newspaper is your last resort service. You must first attempt to serve bio dad by personal service. Sometimes a savvy process server can get the job done, sometimes no one can find a well-hidden person. If the process server can't find the dad, you move the Court for leave to serve by publication. That's the pages and pages of tiny legal print you see in the classified section; each is a service by publication.

Just a thought: Bio dad might come out of hiding long enough to accept service, sign the Consent to Adoption, and have his signature notarized. If you have any clues where he might be, you could ask friends/relatives in the area if they would help you get the documents to him. All he would need to do is step out long enough to accept the documents from the server, sign them, and hand them back. Then Process Server could file the Certificate of Service attesting proper service, and sent the documents to you. Long shot, but it takes bio father off the hook he's been hiding from.