Linux

Elixir checks most of those boxes. If you want a good functional scriptibg language, Elixir soynds like the go to. Some lisp language like guile should also be sufficient, and probably have a lighter footprint.

This requirement stands out though:

has a simple/straightforward setup (ideally, it should be a single executable that I can just copy to a remote system, use to run a script and then delete)

Thats basically what ansible does. If you plan on doing this to multiple machines you should just use ansible. Also how do you plan on ensuring the scripting interpreter is installed on the machines?

https://nim-lang.org/

Perl would be my candidate for more advanced text handling than what sh can do.

Never used Lua but I think it's fun.

If nothing else works, just learn C/Rust. There's plenty of that on Linux systems, I think you'll be able to manage. Yes, it doesn't meet a lot of your requirements.

Quickly came to write "AWK!!!!!!!!!" but yeah... you don't want its superiority... 😜

Why not give (Common)LISP a try?

posix sh + awk for manipulating data?

You should probably check out Guile.

Why does it need to be a scripting (by this I assume interpreted) language? For your requirements - particularly lightweight distribution - a precompiled binary seems more appropriate. Maybe look into Go, which is a pretty simple language that can be easily compiled to native binaries.

You could use Ansible for automation just keep in mind it needs python.

Bro seriously just slap pyenv + pyenv-virtualenv on your systems and you’re good to go. They’re absolutely trivial to install. Iirc the latter is not a thing in windows, but if you’re stuck on windows for some reason and doing any serious scripting, you should be using WSL anyways.

Could use a hipster shell like fish, nushell or elvish. I know the latter two have the functional support you're looking for.

It is possible to wrap something like python into a single file, which is extracted (using standard shell tools) into a tmpdir at runtime.

You might also consider languages that can compile to static binaries - something like nim (python like syntax), although you could also make use of nimscript. Imagine nimscript as your own extensible interpreter.

Similarly, golang has some extensible scripting languages like https://github.com/traefik/yaegi - go has the advantage of easy cross compiling if you need to support different machine architectures.

perl might be on all your systems. It’s kind-of a legacy, but still actively developed. It’s not a great language: it looks like bash scripting on steroids. But if you just need to write some small scripts with a language more powerful than awk or bash, it does the job. If perl isn’t on all of your systems already, then I would choose a better scripting language.

vlang might fit your request pretty nicely. It's a bit patchy in places but mainly stable and gets pretty frequent updates