opam binary package in Ubuntu Focal armhf

 OPAM stands for OCaml PAckage Manager. It aims to suit to a vast number
 of users and use cases, and has unique features:
  * Powerful handling of dependencies: versions constraints, optional
    dependencies, conflicts, etc.
  * Multiple repositories backends: HTTP, rsync, git
  * Ease to create packages and repositories
  * Ability to switch between different compiler versions
 .
 Typically, OPAM will probably make your life easier if you recognize
 yourself in at least one of these profiles:
  * You use multiple versions of the OCaml compiler, or you hack the compiler
    yourself and needs to frequently switch between compiler versions.
  * You use or develop software that needs a specific and/or modified version
    of the OCaml compiler to be installed.
  * You use or develop software that depends on a specific version of an OCaml
    library, or you just want to install a specific version of a package, not
    just the latest one.
  * You want to create your own packages yourself, put them on your own
    repository, with minimal effort.

Source package