GitHub Copilot nvim plugin[1] has autocomplete with ghost text, but of course it requires you use GitHub Copilot :)

[1]: https://github.com/github/copilot.vim

Nvim 0.12 (prerelease) also has ghost text with the "textDocument/inlineCompletion" LSP server capability[1]. Currently supported by the "copilot" config[2], but any LS that supports "textDocument/inlineCompletion" can be used (and the config[2] shows optional QoL improvements).

1: https://github.com/neovim/neovim/pull/33972

2: https://github.com/neovim/nvim-lspconfig/pull/4029