Is Audit plugin available for Community edition?
Based on your error, you just need to grant the insert privilege to the 'root2' user:

GRANT INSERT ON *.* TO 'root2'@'10.80.16.236'


(you'll need to modify this based on your actual 'root2' user)

In terms of whether there is a plugin available, technically the mysql audit log plugin is only for the enterprise edition, and not the community edition.

That said you can usually use the one supplied by Percona or Mariadb with MySQL (there may be others).

I use the Percona one with my 5.5 databases, and the Mariadb one with my 5.7 databases, as I couldn't get the Percona version to work with 5.7.

You install them in exactly the same way. Download them, and place the file in your plugins directory first,then 

Percona
    INSTALL PLUGIN audit_log SONAME 'audit_log.so';  

Mariadb
    INSTALL PLUGIN audit_log SONAME 'server_audit.so;