RPC and thus OpenAMP are officially supported on GIGA however it generates this compile time Warming in IDE 2.3.6 using GIGA Boards 4.2.4

WARNING: library openamp claims to run on mbed, mbed_portenta, mbed_nicla, mbed_opta architecture(s) and may be incompatible with your current board which runs on mbed_giga architecture(s).

To avoid this warning I added mbed_giga to the architectures line in the library.properties file for the open amp library in GIGA boards

I consider myself to be unqualified to make such a change on GitHub...