The early Linux distributions had a sort of package repositories (e.g. Slackware). Earlier you could get sources for Linux-hacked stuff on some places (forget details, that was 1992 or so for me).
Earliest repositories (source) were e.g. the GNU mirrors (starting around 1985 or so), public FTP (and gopher) sites were plenty by 1990 (and probably much, much older). Binary packages were not popular, due to wild differences in architecture/operating system/setup common in the '80s. A common way to share sources (for non-Internet connected sites in the '80s) were Usenet groups like comp.sources.unix (got my first version of Perl as thirty-something posts you had to unpack an stitch together just right, configure by futzing in Makefile macros and then --hopefully-- build.
First mention of software sharing I've seen documented was the custom of dropping off tapes with interesting stuff at DECUS (DEC User group) conferences, and pick them up with a compilation of everything contributed at the end. I believe IBM users had something similar going too. This was in the '70s or even earlier (sorry, away on vacation, no access to my computer now).