You’ll need an original iPod, iPod Mini, or iPod Video or Classic for Rockbox compatibility. iPod Touch is just an iPhone without the phone, so it’s locked into iOS, but the original iPod, and iPod Mini, Video, and Classic all support Rockbox.
I presume any generation of iPod Shuffle or Nano is also locked into Apple firmware.
There might be some cases even for single-player games where DRM platform-locks you into Windows but that’s rare from my understanding.