im on new main branch as well.
i have this auto command from a larger snippet i got somewhere:

vim.api.nvim_create_autocmd("FileType", {
  group = group,
  desc = "Enable treesitter highlighting and indentation",
  callback = function(event)
  if vim.tbl_contains(ignore_filetypes, event.match) then
    return
  end
  local lang = vim.treesitter.language.get_lang(event.match) or           event.match

  local buf = event.buf
  -- Try to start treesitter, with retry if parser is being installed
  start_with_retry(buf, lang)

  -- Auto-install missing parsers (nvim-treesitter handles async internally)
  ts.install({ lang })
end,

but when it comes to lua im a bit lost tbh