OTP is a work in progress available in the gleam_otp [0] package, supplemented with the lower level gleam_erlang [1]. Or you can call OTP things manually with FFI.
This is what I wrote regarding using otp in gleam. One of the issues I'm working on next is to send typed messages to processes, which has me a little stumped.
At the moment the typed channels work, you can't register () a channel or a pid.
I will likely continue working on this document once I have my current project completed.