I haven't spent any time with Fennel, but it seems more promising to me.

I couldn't get comfortable with Hy. It drops so many lispy things, such as let statements and persistent data structures, in order to stay close to the Python substrate. (You can get both from libraries, but at the cost of easy interop with Python packages, which kind of defeats the whole point of being on the Python platform in the first place.) It ultimately came out feeling less like I was working with a lisp, and more like I was working with an s-expression syntax for Python.

OTOH, if you think that Python, while otherwise great, is really suffering for lack of defmacro, Hy absolutely succeeds in getting you Python with defmacro.

I ended up dropping Hy very soon after they dropped let. Had an entire blog engine written in it: https://github.com/rcarmo/sushy

...but I wanted Hy to be LISP, not a thin veneer over Python.

There is another small lisp that targets both Lua and Javascript called "lumen"[1]. Small enough that you can easily tinker with it. I added clojure style {} literals to the reader and paired it with hyperapp to write a toy web application.

[1]: https://github.com/sctb/lumen

If you are interested in LISP variants, check my "catalogue" over at https://taoofmac.com/space/dev/LISP

Plenty of lisp frontends for lua, see https://github.com/hengestone/lua-languages#lisp