camlp5 binary package in Ubuntu Focal arm64

 Objective Caml (OCaml) is an implementation of the ML language,
 based on the Caml Light dialect extended with a complete
 class-based object system and a powerful module system in the
 style of Standard ML.
 .
 CamlP4 is a Pre-Processor-Pretty-Printer for Objective Caml. It
 offers tools for syntax (Stream Parsers and Grammars) and the
 ability to modify the concrete syntax of the language
 (Quotations, Syntax Extensions).
 .
 This package contains the "classical" version of CamlP4
 executables and libraries for pre-processing and pretty-printing
 OCaml sources both interactively and in a batch fashion. The
 "classical" version is the implementation of CamlP4 which used
 to be distributed with OCaml before the release of version 3.10.

Source package