If you have the PlayStation 4 disc version of Resident Evil 2, the PS4 disc must be inserted into the PlayStation 5 system to launch and play the PS5 upgraded version. As such, a PlayStation 5 with an Ultra HD Blu-Ray Disc Drive is required to play the upgraded version of the PlayStation 4 disc version.
For more information, please visit the PlayStation help article:
Upgrade an eligible PlayStation®4 game to the digital PlayStation®5 version