Yamaha's official support provides firmware updates (like V1.30) and manuals for the physical keyboard, but not Kontakt-ready sound files.
While various "free" links circulated in 2021 on platforms like YouTube and Facebook, users should exercise caution: yamaha psr s900 kontakt free download 2021
The Yamaha PSR S900 Kontakt library is a collection of high-quality sounds and instruments sampled from the Yamaha PSR S900 keyboard. This library allows users to access the keyboard's sounds and features within Native Instruments' Kontakt software, which is a popular platform for virtual instruments. Yamaha's official support provides firmware updates (like V1