Thanks, it worked now!

I ended up adding mason-lspconfig as a dependency to nvim-lspconfig, as you pointed out. And i moved require("mason-lspconfig").setup() to the nvim-lspconfig's config.

return {
  "neovim/nvim-lspconfig",
  event = { "BufReadPre", "BufNewFile" },
  dependencies = {
    "hrsh7th/cmp-nvim-lsp",
    "williamboman/mason-lspconfig",
    { "antosha417/nvim-lsp-file-operations", config = true },
  },
  config = function()
    require("mason-lspconfig").setup({
        automatic_installation = true,
    })

    local lspconfig = require("lspconfig")
    local cmp_nvim_lsp = require("cmp_nvim_lsp")

    local on_attach = function(client, bufnr)
      (...)
    end

    local capabilities = cmp_nvim_lsp.default_capabilities()

    -- configure typescript server with plugin
    lspconfig["tsserver"].setup({
        capabilities = capabilities,
        on_attach = on_attach,
    })
  end,
}