Haskell tooling went from awful to best in class after stack came out. Look for “Quick stack method” in the installing page- It should be easy to build from source now with just a few commands. No doubt will take a long time to compile all the packages and you might still have issues tracking down any non-Haskell dependencies (c libraries).

this got replaced with ghcup iirc

Pandoc is really easy to build with just Haskell and Cabal installed via ghcup, without needing any Haskell packages from your distro.

It or one of its libraries did not compile for me OOTB in Gentoo. Granted it's marked as nonstable (~*). That's unfortunate, because I really liked to use it when I was mainly running Debian. Though I didn't really put any debugging effort into making it work.

I did this years back, it took, ehm, quiet some time. I use a binary now :D ISTR it starts with building a self-hosting Haskell compiler...

Yeah, I ended up upgrading my machine's ram when I was building it from source. It's sizable.