I'm playing around with Rakudo Perl 6 lately and was searching for a project similar to CPAN. I found CPAN 6, but I think there is no Perl 6 code yet.
So I'm looking for some alternative that does not necessarily aim to be a long term solution, but is capable of maintaining modules and is written in Perl 6.
As Rakudo development goes it might be possible to create more complex Perl 6 code soon.
Your first stop for Perl 6 modules should be https://modules.raku.org/.
Modules should be installed with zef.