Hello Dik, thanks for all you explained about REST API: I'm going to try it ASAP to gather as much info as possible.
Since I'm not sure why the Global Status LED is Amber On...to better diagnose this situation I'll also try to disable fastboot (no fastboot) - it should be enabled by default - and, once the fastboot is disabled, I'll reboot the Aruba 8320 to let it to perform POST diagnostic during booting process (Front-end Port Loopback and Register Read/Write tests)...this will also let me to watch any useful message (I hope) at console...in any case, once ArubaOS-CX has booted, via show selftest command I should be able to see more complete diagnostic results (I learned that, irrespective of fastboot status, only the Register Read/Write test happens each time at boot...instead Front-end Port Loopback tests are done only if fastboot is disabled otherwise they are skippped, that probably make sense causing the boot to be fast <- documentation uses an example that, if I'm not mistaken, is saying exactly the contrary [*]).
[*] Aruba 8320 Diagnostics and Supportability Guide for ArubaOS-CX 10 Edition 1 June 2018, sheet 83 (Example when fastboot is disabled).