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
The PS5 Could be Backwards Compatible with Games from Older Models - Digital Overload
PS5 Backwards Compatible PS4 Game Discs Confirmed Supported
PS5 Backwards Compatibility: Can You Play PS4 Games on PlayStation 5? | Push Square
PS5 Won't Be Backwards Compatible With PS3, PS2, or PS1 Games
Can you play PS4 games on PS5? Is PS5 backwards compatible? | Gaming
Sony Files Patent that Points to PS5 Being Backwards Compatible with PS4, PS3, PS2, and PS1 - YouTube
Why You Should Buy A PS3 (Backwards Compatible) With A PS5 - YouTube
PS5 Backwards Compatibility Database Catalogues Improvements And Performance Of PS4 Games On Sony's New Console - PlayStation Universe