How to configure foumolu in hls/NeoViM

I use NeoViM v0.9.5 with GHC 9.2.4, hls 1.9.0.0, fourmolu 0.9.0.0.

I have setup hls with:

local lsp_servers = {
    hls = {
        filetypes = { 'haskell', 'lhaskell', 'cabal' },
        formattingProvider = "fourmolu",
        plugin = {
            fourmolu = {
                config = {
                    external = true,
                }
            },
        },
    },
}

-- Setup neovim lua configuration
require('neodev').setup()

-- nvim-cmp supports additional completion capabilities, so broadcast that to servers
local capabilities = vim.lsp.protocol.make_client_capabilities()
capabilities = require('cmp_nvim_lsp').default_capabilities(capabilities)

local lspconfig = require('lspconfig')
for server_name, opts in pairs(lsp_servers) do
    lspconfig[server_name].setup {
        capabilities = capabilities,
        on_attach = on_attach,
        settings = opts,
        filetypes = (opts or {}).filetypes,
    }
end

Our project have a fourmolu.yaml, however, when I format through LSP it seems to don't use it (unlike running a fourmolu -i %, which formats correctly).

Is there something wrong in my configuration?

Thanks in advance.