I second Pianoteq as a recommendation. It can run on Linux, so I have it on a Raspberry Pi attached to my digital piano. As a bonus, it also drives some addressable (programmable) LEDs: https://github.com/whyboris/Digital-Piano-LED

To install Pianoteq on a Raspberry Pi, it's a single script that sets everything up: https://github.com/youfou/pianoteq-pi