coc-calc VS completion-nvim

I'm currently in the process of getting rid of CoC.nvim and moving to NeoVim 0.5 builtin LSP and Lua plugins. One of the CoC plugins I was using was coc-calc, which is essentially a completion interface to a calculator - you type the math expression with = and invoke completion and coc-calc will write the result of the expression as the completion "match".

I think it can be on any lua file. Plus I checked completion.nvim is now on archived.

You don't, nvim-cmp sets up you. Jokes aside, I am using completion-nvim. Unfortunately it got abandoned just as Neovim 0.5.1 got released, which contained a breaking change. You can look into the pending PRs to see how to fix it for yourself, just use one of the fixed forks. It really sucks, but unless someone steps up an creates a new completion plugin that's what I am stuck with.

I couldn't figure out how to change this. I found some options, some of which made an entire split window appear above... that's hideous. I also found this, but that works with lua. How do I even set up these lua scripts? I don't get it. Can I get some guidance? Thanks.

I have tried to move to nvim-cmp since completion-nvim is dead, but for the life of me I cannot figure out how to make it not automatically select the first completion candidate. If I type date and hit to insert a new line, cmp takes as the "confirm selection" key (because I have mapped it that way) and expands the snippet. I only want to confirm a selection if I actually selected something from the menu. completion-nvim may be dead, but at least its author had the courtesy to write down how to use it in complete plain English sentences instead of broken English one-liners. Eventually I gave up and moved back to the old setup.

That will give you the basics, you should see linter diagnostics and auto omin completion should work. For better auto-completion and snippets you can set up one of the completion- and snippets plugins. Personally I use completion-nvim and Ultisnips. There may be better plugins out there, that's just what I happen to have installed.

I recently upgraded from Neovim 0.5.0 to 0.5.1 and LSP autocompletion stopped working. I'm using https://github.com/nvim-lua/completion-nvim but it looks like its maintenance could be much better. I'm looking for some alternative but I'm not sure what would be a good choice for LSP. Any recommendations?

I'm trying to configure completion-nvim with Neovim's LSP, but am not getting any sort of pop-up/display.