In the FWIW department, my (tiny indie games) company shipped several apps based on S7 that ran cross-platform on iOS & Android (together with SQLite). We used native UI, but had a common Scheme S7 core that had the game and database logic. It was marvelous for succinct code, fast running tests and really helped slim down duplication across our previously completely native apps. The "single C file" was critical to our choice, as, like SQLite, it enabled us to easily integrate with the native iOS & Android tooling without setting up byzantine build processes.

We also used Guile during the desktop-based development process for sometimes better debugging and to enforce greater R7RS code-compatibility. (Ah, and the subtle bugs of alternative function parameter evaluation order!)

We later moved to Fennel(-lang) based on Lua as it was a slightly better fit for our team in various ways, but the S7 experience, including the community, was fantastic!

Both solutions proved stable with tens of thousands of monthly active players.