If following the Dark Brotherhood attack, speaking to a guard on the mainland, they will redirect the player to Senillos Tulnus in Firewatch, who in turn will redirect the player to Garros Mellorus. However, these still trigger the Vanilla journal entries, asking the player to go to Appelles Matius and Asciene Rane, which is both misleading and confusing. I suggest adding new entries to the journal for the Tamriel Rebuilt-specific path of this quest. If the player later chooses to speak to a guard on Vvardenfell about the attacks before going to Mournhold, it wouldn't hurt to add the original topic as well.