Extremely outdated install instructions.

[navid-zamani]

Overlays haven’t been a thing in Gentoo for many years now.
It’s repos (repositories) nowadays.

Shouldn’t simply enabling the repo via eselect repository enable haskell and then emerging hackport be enough to get everything working? (The only question left would then be where the ebuilds go. Aka selecting one of your local repos. … The current instruction of putting Just (LocalInfo {distfiles_dir = "/var/cache/distfiles", overlay_list = ["/var/db/repos/haskell"], portage_dir = "/var/db/repos/gentoo"}) in ~/.hackport/repositories seems to not be suited to work with repos, given that it still says overlay_list and portage_dir. Hackport should be able to read that from /etc/portage/repos.conf and /etc/portage/make.conf`. )

I`m unsure if hackport is deprecated or abandoned nowadays and I haven’t heard about it due to having been away from Gentoo since 2017. (But even back then, overlays were already replaced by repos.)

[hololeap]

Yes, the line in the readme is quite old (from 13 years ago), but it should be understandable even if it's using an old term. Hackport needs to know where to place the ebuilds it generates, which is usually the repo named haskell, but possibly not. I'm not sure how it would get this information from repos.conf except by guessing. The method of selecting a repo location could probably be improved.

I`m unsure if hackport is deprecated or abandoned nowadays

I'm not sure where you're getting this idea from. There isn't much activity, but the last commit was only three weeks ago.