Description of problem: This bug is opened in relation to a feature request for support of blowfish crypt in shadow/passwd files. libuser should support blowfish in addition to crypt. Cf: https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=173002
lib/user.c will have to create 128 bits of salt (not just 128/6 characters), not separated from the hash with $. Can't be tested without glibc support, though.
The glibc maintainer decided blowfish support will not be added, see https://bugzilla.redhat.com/show_bug.cgi?id=173834#c2 . Rawhide libuser-0.56.7-1 supports SHA256 and SHA512.