Are there any rough estimates on popularity of lua implementations? At this point it feels lua means luajit

not even close, because there are a lot of places where you can't run LuaJIT

Where can you not run LuaJIT? Genuinely curious

Wasm and platforms like iOS and Nintendo Switch (I think).

anywhere that does not allow self modifying code such as app stores.

LuaJIT is not just a JIT, it also includes high speed interpreters for x86, Arm, and more.