I've used platformio and it works well. It can generate ‘compile_commands.json’ and clangd lsp works out of the box.

I wrote a small program for the arduino nano 2 years ago, it isn't that fancy, a quickly hacked together led flash animation, but the Makefile works. You really just have to install the dependencies and adapt it for your project and it should work.

I've tried many times for a few years now to get this working. Even though I get platformio to create a compile_commands.json it still doesn't work very well. Thinks std::string is a uint_8 and so on. I've just given up on it and use VS Code to program the ESPs I work with. Use neovim for everything else.