I wasn't trying to copy binaries over but I found a very specific thing that doesn't work with musl and libnss. System Services Security Daemon (sssd) which coupled with authentik would have made automated ssh logins on remote servers a manageable thing cannot work on alpine. It does work on Void which made me think they must have solved the musl situation but no, apparently Void has a glibc variant and it only works there.

Interestingly there is an sssd package in alpine but it cannot work. https://gitlab.alpinelinux.org/alpine/aports/-/issues/16969

https://github.com/rustadopt/uzers-rs/issues/20 ("Now the bad news: I poked around a bit and believe the problem is that MUSL does not support sideloading the NSS plugins needed to retrieve things from SSSD like GLIBC does and thus does only ever read users from /etc/passwd, see: SSSD/sssd#6586")