First, you must edit current configuration on MikroTik SNMP. Do this command:
> snmp community print
Flags: * - default
# NAME ADDRESSES SECURITY READ-ACCESS
0 * public ::/0 none yes
> snmp community set numbers=public encryption-password=CHANGETHISPASSWORD encryption-protocol=AES read-access=yes security=authorized authentication-protocol=SHA1 authentication-password=CHANGETHISPASSWORD name=public
Test your configuration using this command:
> snmpwalk -u public -v 3 -a SHA -A CHANGETHISPASSWORD -l authPriv -x AES -X CHANGETHISPASSWORD 1.3.3.7
If it's work, add new host to your LibreNMS using this command:
./addhost.php 1.3.3.7 ap v3 public CHANGETHISPASSWORD CHANGETHISPASSWORD sha aes 161 udp
Reference