After the quick loading screen with the hat the specialk overlay vanishes, I’m trying to set up HDR, I can quickly select the option if I’m fast enough, but then I just get a black screen, and I am unable to configure further because the overlay isn’t there.
Persona 5 Strikers swaps to a different DirectX version for cutscenes, which confuses SpecialK. You need to go into SpecialK’s INI and find where all the different Graphics APIs are listed and disable all but DirectX 11.
SK cannot even detect the game due to a combination of Denuvo and shipping a generic executable called game.exe 
I’d apply those compat overrides automatically otherwise.