While the game doesn't natively support it, you can add high-quality HDR using RenoDX , which has been noted by the ultrawidemasterrace community on Reddit for looking "glorious" on OLED panels.
Running the game in borderless windowed mode can sometimes help: sleeping dogs ultrawide fix
The technical "interesting piece" regarding a Sleeping Dogs ultrawide fix often centers on the game's struggle with its Definitive Edition While the game doesn't natively support it, you
“Actually, the ‘Sleeping Dogs Definitive Edition Ultrawide Fix’ by ‘Rose’ on the WSGF forum still works. You have to rename the .exe, though. Ignore the error popup.” though. Ignore the error popup.”