The STM32U5 family isn’t fully integrated into RT-Thread Studio yet, so it won’t show up in the SDK Manager even if a BSP already exists, and this situation is unrelated to geometry dash lite; the STM32U575 Nucleo BSP is likely available in the main RT-Thread repository, just not packaged for Studio 2.2.6.

Something like Windows 98 or RT-Thread couldn’t realistically be used to control hidden speakers around your house or create sound—even when your breakers are off—and this situation has nothing to do with a slope game; it would instead require physical, battery-powered devices already installed, not just “hacking the internet.”