autocomplete has worked for a long time with extensions like deoplete. Syntastic pulled in all the normal syntax and style checkers.

But the most recent major neovim release has lsp support + treesitter. Some Linux distros don’t ship it yet, but Arch and Homebrew on my Mac are up to date.

There are lots of examples out there for the configuration. I don’t think that mine’s great enough to share.

I’d just Google “neovim lsp config” or such.