Recently there's an influx of “PS5 backwards compatible” articles on google reporting it will play ps1 through ps4 titles. If it's true, much respect to Sony. : r/PS3
How to play PS2 and PS3 games on PS4? Sony PlayStation backwards compatibility explained - Daily Star
PS4 backwards compatibility: Can You Play PS1, PS2, and PS3 Games on PS4?
PS5 backwards compatibility will cover all PS2, PS3, and PS4 games according to Turkish retailer - NotebookCheck.net News