Yeah, this is crucial to me. I was formerly a paid user of ST3 before switching to VSCode, but gave the ST4 beta a try a month or so ago. I couldn't get the LSP to work for me for Elixir, so I ended up back on VSCode for now.
I figured I'd wait until the non beta release, and try again.
The sort of minimal deal breaker level of support for me is being able to jump to definition. The symbols, if I understand correctly, are based on the syntax configuration, and for the common Elixir one, it includes the type definition line, each function head, and the callsites of the function, which makes it nearly useless for symbol navigation.
I figured LSP would help in this regard, but I couldn't make it work. The docs were vague, and I think I had to put some JSON configuration structure in some file, but nothing I tried I guess was the right file or right structure.
Still, I love everything else about Sublime and am excited now for multi-tab-select, so I'll probably give it one more try. Hopefully LSP is better integrated or documented by now.