> I would have loved for Vim to also adopt Lua
Vim has supported Lua for a long time. Anyone who wants to really use Lua for Vim plugins already has the option of doing so.
How does that compare to writing Lua plugins for Neovim? Seemingly all search results for "write vim plugin in lua" are dominated by results for writing lua plugins for neovim. Does vanilla Vim have something like Neovim's "Remote Plugin" or how does it work?
But for the stuff that is available, you can either use the vim help to learn about it or search on vim's github issues / PRs, e.g. https://github.com/vim/vim/pull/7959. I'm curious if there are other ways to learn more about vim's lua interface, searching on google as you said does not give great results for vim, just neovim.
Really not sure why you would want to though
:help Lua