nix-dotfiles VS neovim-rust

You can check mine out. There are also some here

You can also try my full config: https://github.com/mjlbach/nix-dotfiles/blob/master/nixpkgs/configs/neovim/init.lua

I do, in fact, use expandtab

Here's my init.lua. Neovim nightly will read this by default if you place it at $HOME/.local/share/nvim/init.lua. I use this configuration on the neovim source (c/lua) with clangd and sumneko language server, and on projects for research (python mostly), amongst other things.

Not yet! w is window and o is options. You can check out my init.lua for most of the common ones.

For autocompletion, I recommend completion.nvim. Here is the pertinent part of my init.lua (uncomment require'completion'.on_attach()), but you can wrap this in a lua heredoc if you're still using an init.vim.

Which server? Here is a minimal init.lua and my personal init.lua

You're not actually using any of those channels. You need to overlay the channels onto your package set. If you hop on the IRC or discord we can work through your specific error message, but here is how I have it configured (with home-manager):

https://github.com/mjlbach/nix-dotfiles/blob/5f956f9548bdf7f9c954c926e6ab24e94c4bf55d/nixpkgs/configs/neovim/init.lua#L380-L425

If you're looking for a sample config, I recommend this one: https://github.com/sharksforarms/vim-rust/blob/master/neovim-init-lsp-compe-rust-tools.vim

I tried neovim-init-lsp-compe.vim and neovim-init-lsp.vim from these minimal configs but no luck. I currently am all drained trying to debug my issues so might live with it or go back to vscode or coc. But I really really appreciate the work you guys do!

And the repo for examples: https://github.com/sharksforarms/vim-rust