Rental expenses prior to in service date

I have a seen a view posts on this topic but want to get an exact answer for my situation if possible.

I’ve seen posts saying that you cannot use the de minimis rule for expenses that occurred prior to the property in service date. My goal is to use the de minimis safe harbor to deduct expenses for furnishing my Airbnb.

My scenario is a bit complicated. I bought a house to be my primary residence that has a second dwelling that I have always planned to use as a STR. The STR is ready to go besides needing some furniture and a STR permit. Is there a scenario that my Airbnb portion of my house could be considered in service before I advertise it? As in, if I get my STR permit would that count it as being in service and thus I could use the de minimis rule?

Any help on this topic would be greatly appreciated!