Unfortunately, it is not possible to use Rune Audio with Raspberry Pi Pico as it is not a full-fledged single-board computer like Raspberry Pi 4. Raspberry Pi Pico is a microcontroller board that is designed for low-level tasks and does not have the capability to run a complete operating system like Linux.
Additionally, Rune Audio is designed specifically to work with Raspberry Pi models that have built-in network connectivity like the Raspberry Pi 4, which has Wi-Fi and Ethernet capabilities. Without these capabilities, it would be difficult to use Rune Audio on a Raspberry Pi Pico.
However, there are other audio player solutions available that are specifically designed to work with microcontrollers like the Raspberry Pi Pico. You can consider exploring these options and find the one that meets your requirements.