There is a huge ecosystem of small handhelds that either run Linux or Android. For example the Anbernic RG35XX is incredibly cheap and a great form factor. Or a

There is a huge ecosystem of small handhelds that either run Linux or Android. For example the Anbernic RG35XX is incredibly cheap and a great form factor. Or a Miyoo Mini. The Switch Lite is also more appropriate for a 7yo size-wize, but it's still no gameboy pocket. I think there's a big Anbernic sale happening right now, coincidentally. I find the idea of a real, handheld Pico-8 pretty compelling. Alternatively for music there's kid-oriented products like the Yoto player, which is pretty DRM heavy but fairly customizable. edit: I see you're already aware of the SBCs. Whatever you choose, it'll be great.