The GUI package manager is "HaikuDepot" and the command-line tool is "pkgman". HaikuDepot is documented in the Userguide: https://www.haiku-os.org/docs/userguide/en/applications/haik... Dunno why no search engines took you to it.

Also dunno why WebPositive wouldn't do anything for you. It's still a little buggy, but it usually works well enough for my purposes...