I like this question because it asks about a genuine need where a "hole" exists.
Foremost the FSF maintains a directory [1]
Of course there have been, and are, many means by which you can find of amazing free open source software on the web.
Back in the Slashdot days "Freshmeat" and "Sourceforge" [2] were the go-to places, but were eventually strewn with the weeds of advertising and low quality submissions unfiltered for malware.
Web indexes remain but YMMV wrt quality, and many can be considered link-farms.
In some sense "distros", and those people working to curate collections are doing that work.
But discovery is still unsolved in many ways. A big threat (in my personal opinion) is the gravity of GitHub (part of the Microsoft estate) pulling in so many small developers and creating an over-reliance on patronage hostile to the free software charter.
It would be interesting to ponder what more modern social networks could offer, particularly from the revenue/funding POV for paying for quality curating and review,