Lua 5.4 was released on 29 Jun 2020. Its main new features are a new generational mode for garbage collection and const and to-be-closed variables.
The current release is Lua 5.4.3, released on 29 Mar 2021.
http://www.lua.org/manual/5.4/readme.html#changes
http://www.lua.org/manual/5.4/manual.html#8