brittany VS hindent

You will also need a formatter that uses that style. Brittany for example. The default formattingProvider for HLS is ormolu, which I believe doesn't use this style, so you will have to change this setting.

Yeah I couldn't find anything at all which is really unfortunate. You could check out the config source code

Turns out I prefer Brittany to Ormolu, I edited it so it hopefully looks less verbose all on one line

I use Brittany and prefer it to Ormolu, because it aligns more things and it break lines that are too long automatically. I have recently tried to figure out how I could implement a solution to https://github.com/lspitzner/brittany/issues/157, but it is quite hard to figure out which parts of the code would be involved in such a change. And I don't really have enough time to make steady contributions, but I will probably try to make a few contributions sometime.

Because every language is so different, every language requires individual care. So there are language specific formatters (https://github.com/mihaimaruseac/hindent for Haskell), which are usually configurable by some configuration file the in the project.

In the long run, though, I expect Fourmolu (not Ormolu) will end up becoming the norm, because, really, two-space indents are not going to work for everyone. One of the things I like about hindent (that I did myself) is that it discovers default language extensions from the .cabal file, so you don't need to specify those yourself. I might see if I can get that code into Fourmolu.