This is covered in the docs
https://docs.oracle.com/cd/E63000_01/EMBSC/install_agent_new.htm#EMBSC373 "6.2.2 Installing a Standalone Oracle Management Agent 13c Release 1 Using Add Host Targets Wizard or EM CLI"
Multiple platforms are included with the OEM software no matter what *it* it is running on, eg
$ORACLE_HOME/bin/emcli login -username=sysman
Enter password : Login successful
$ $ORACLE_HOME/bin/emcli sync
Synchronized successfully
$ $ORACLE_HOME/bin/emcli get_supported_platforms
-----------------------------------------------
Version = 12.1.0.5.0
Platform = Microsoft Windows x64 (64-bit)
-----------------------------------------------
Version = 13.2.0.0.0
Platform = Linux x86-64
-----------------------------------------------
Version = 13.2.0.0.0
Platform = Microsoft Windows x64 (64-bit)
-----------------------------------------------
Version = 13.2.0.0.0
Platform = Oracle Solaris on SPARC (64-bit)
-----------------------------------------------
Version = 13.1.0.0.0
Platform = Microsoft Windows x64 (64-bit)
-----------------------------------------------
Version = 13.2.0.0.0
Platform = Linux x86
-----------------------------------------------
Platforms list displayed successfully.