Your TeX installation now has two variants of the LuaTeX engine:

  • miktex-luatex is the default engine with Lua 5.2 inside
  • miktex-lua53tex is the new engine with Lua 5.3 inside

By default, the LuaTeX executables (luatex, lualatex, ...) are linked to the 5.2 engine. Running luatex --credits will show you:

Compiled with lua version 5.2.4

If you want, you can link the LuaTeX executables to the new 5.3 engine, also known as luatex53. This is a two step process:

  1. Set the configuration value [luatex]luaver=5.3
  2. Create the links

For example:

initexmf --set-config-value [luatex]luaver=5.3
initexmf --force --mklinks

As always: run initexmf with administrator privileges and add the --admin option, if you manage a shared MiKTeX installation.

Running luatex --credits should now show:

Compiled with lua version 5.3.4

You can switch back to the default 5.2 engine by re-setting the the configuration value:

initexmf --set-config-value [luatex]luaver=5.2
initexmf --force --mklinks