Since the days of Mojave, Apple has tried to protect /usr/bin from user interference.
Now the /usr/bin path exists only for system files and installing custom files there can kill the system, but, user executable files always had the path /usr/local/bin.
To install iasl on the path /usr/local/bin in the terminal, go to the folder where iasl is located (in my case, the iasl folder is on the desktop)
~ % cd /Users/User/Destop/iasl
Next command:
~ % sudo cp iasl /usr/local/bin
And next:
~ % iasl -v
After entering the iasl -v command, we get a system warning that iasl does not have permission to run.
Go to:
System settings > Security
There just iasl will require confirmation to start. We allow it to run
In the terminal repeat:
~ % iasl -v
and we see:
Last login: Sun Nov 22 13:58:33 on ttys000
User@iMac-User ~ % iasl -v
Intel ACPI Component Architecture
ASL+ Optimizing Compiler/Disassembler version 20180427(RM)
Copyright (c) 2000 - 2018 Intel Corporation
User@iMac-User ~ %
PS. Sorry for my english.