liblwt-ssl-ocaml 2.7.1-4build1 (arm64 binary) in ubuntu bionic

 Lwt is a library for cooperative threads implemented in a monadic style.
 Unlike preemptive threads, cooperative threads do not use a scheduler to
 distribute processor time between threads. Instead, each thread must
 announce that it wants to let the others run.
 .
 This package contains runtime libraries for programs using Lwt with
 cooperative OpenSSL.