Maybe it's too early for me to say this, but the same script hole is still in the game.
I know that it is the typical game that is not canonically incestuous but is written as if it were, and that technically it is not a script hole in itself to use that writing technique, since the relationship between Frank, Debbie and Dianne is quite similar to that of Grace Odette and Tuuku (friends who are practically family), but the same doubt remains in the air, where did Frank and Annon live before the game started?
Apparently Debbie's house has no more rooms to argue that they lived there as guests, plus I highly doubt that he slept all this time on the couch or in his son's room, and I also don't think he shared a room with Debbie being alone. "friends". Everything leaves us with the following options: either Dark Cookie modifies Debbie's house again to include an extra guest room, or gives her her own apartment in the building with Tonny, Becca and the other people; In either case she would have to modify the main story, since they would have to include this place when looking for clues about Frank's death. The other alternative to this would be to turn Debbie into Frank's second wife and Annon's stepmother, but from what I see this option has already been ruled out (I don't know if it's due to patreon rules or if the developers simply didn't want to use that option)
but hey, I think I'm just getting ahead of the facts, maybe in the future we'll be told that Annon was Becca and Tonny's neighbor (although Tony's story before this update makes it clear that he didn't know the protagonist before saving him of the gangsters), that Frank's secret room magically appears in Debbie's house or that perhaps he lived in the attic all this time and that they left him in his current state after he passed away.
ps a lot of text