Docstring of mapcan tells:

Probably introduced at or before Emacs version 26.1.

The "before" might be deleted, as

 GNU Emacs 25.3.1 (x86_64-pc-linux-gnu, GTK+ Version 2.24.32) of 2022-06-08 fails with

Debugger entered--Lisp error: (void-function mapcan)