Man that seems like an awful lot of ceremony for a trivial web app. Surely the language known for macros and building your own DSLs has a more concise way to get a web app up and running?

I use CLOG these days; it's all so easy to get things done.

re: common lisp shines at low-level tasks like microcontroller programming

While I couldn't find an explicit declaration of this in the linked article, the tunnel system likely has something on the level of an SBC (think raspberry pi) rather than a microcontroller. Common Lisp makes it possible to do fun low-level assembly stuff but AFAIK none of the implementations can run on a microcontroller.

There's uLisp, which builds on Arduino's libraries but it isn't a Common Lisp implementation.

In terms of bare-metal CL implementations there is Movitz (stopped development) and Mezzano, but I don't think those can run on any microcontrollers.

There are also some libraries to convert CL to C, thinlisp and CLiCC, but these aren't actively maintained currently.

The possibility of porting Clozure CL to the RP2040 was discussed in the ccl mailing list last year, but I don't think anyone's working on it.