Persona 5 Royal has a lot of DLC, 45 of them to be exact. Thankfully you shouldn't need to cough up any extra cash for them, as Atlus has confirmed they'll all be bundled into the Windows version of the game.
It's worth noting that the news only explicitly mentions the Xbox and Windows version of the ports, not the Steam version. This might mean the offer is only on the table for those who play the game through Game Pass or the Microsoft Store, which'll be a huge bummer. Hopefully Atlus is just using Windows as an umbrella term and the Steam version will be offered the same treatment.
The game's DLC ranges from things like costume packs to BGM packs to extra personas. There's also a challenge battle mode that has you facing off against Persona 3 and Persona 4's protagonists and some item packs to give your phantom thievery a little boost. You can check out the full list of Persona 5 Royal's DLC on the official Persona website.
Persona 5 Royal launches on Game Pass for PC and Steam on October 21, with Persona 3 Portable set to arrive at a later date. The entire trilogy is landing on Game Pass eventually, but if you're itching for a Persona PC fix now then Persona 4 Golden is currently a part of Steam's Summer Sale.