I cannot use an SSH agent script because the GUI cannot find the path to the SSH public key. I've set things up by the documentation and I've also tried with the user zabbix to zabbix. I can successfully run any ssh script via the CLI, but because of the ITEM "Not supported" error which says "Cannot access public key file /home/zabbix/.ssh/id_rsa.pub/id_rsa.pub". Which is a bizarre path to say the least. If I fully qualify the path in the ITEM, it just duplicates. Since the CLI version works, the ITEM should be configured properly. Here's how I've configured it in the GUI (this is a test script):

Name cpu mon
Type SSH agent
Key ssh.run[cpumon]
Host interface <IP of client>:10050
Authentication method Public key
User name zabbix
Public key file id_rsa.pub
Private key file id_rsa
Key passphrase
Executed script /home/zabbix/cpu_mon.sh
Type of information Text
Update interval (in sec) 30
Flexible intervals No flexible intervals defined.
New flexible interval
Interval (in sec) 50 Period 1-7,00:00-24:00
History storage period (in days) 7
Applications CPU
Enabled