I consider Lua 5.1/5.3/5.4 to be roughly their own language. Somewhat akin to a Python2 vs Python3. Completely manageable transition if you want, but best to stick to an implementation if you can. Within a platform, there are seemingly only ever bug fixes.

NeoVim[0] had a few words on this topic.

0: https://github.com/neovim/neovim/wiki/FAQ#why-lua-51-instead...