To anyone who is lost on this issue, especially with regards to neovim, I found the simplest solution.

Just add the lines to options.lua or any other config file.

vim.lsp.enable("dartls")

This makes use of the nvim-lspconfig plugin which is preinstalled.

And update your Lazyvim distro and Neovim instance.

I still don't have a comprehensive understanding on LSP, but this achieves the goal of effective navigation across my project and to and within Flutter source code.