Cross platform mutex to prevent script running more than instance?

[Malcolm Greene]

Use case: Want to prevent 2+ instances of a script from running ...
ideally in a cross platform manner. I've been researching this topic and
am surprised how complicated this capability appears to be and how the
diverse the solution set is. I've seen solutions ranging from using
directories, named temporary files,  named sockets/pipes, etc. Is there
any consensus on best practice here?
Thank you,
Malcolm