Here a list of almost all the OS distris I've left out:
https://distrowatch.com/search.php?ostype=All&category=All&o...
Besides mentioning Slackware for historical reasons I should have also mentioned NixOS, which I forgot.
The former was the first Linux distri, the later gained some respectable user-base in the last years, I think.
Ah, and there is also Alpine which you can see sometimes here and there. (People using it in containers for reasons I've never understood as that's imho a recipe for trouble.)
But if you look at the rest of the list most of the stuff is really obscure. (I've tried some Solaris derivatives and Exherbo in the past but didn't even heard of all the other names.)
Musl is still a kind of experiment. I would not recommend running experiments in production…
Just a few random links:
https://nickjanetakis.com/blog/benchmarking-debian-vs-alpine...
https://news.ycombinator.com/item?id=28312433
https://www.linkedin.com/pulse/musl-libc-alpines-greatest-we...
https://martinheinz.dev/blog/92
https://www.linuxquestions.org/questions/linux-software-2/mu...
https://unix.stackexchange.com/questions/729342/performance-...
https://github.com/rust-lang/rust/issues/70108
https://news.ycombinator.com/item?id=23080290
https://vector.dev/highlights/2020-07-09-add-musl-and-glibc-...
There are more. Much more of those!
Musl exist in large parts just for ideological reasons. It still rides some hype in industry as industry hates GPL software…