In my suggestion above, I suggested to try a Snom altert info string… This can be used in “Inbound Routs” and/or in the “Ring Groups”
You can try that and see if it is possible to use it with Cisco phones you have. On the other hand, if you know the names of the built-in rings, you can try something simpler
In alert info field of the “Ring Tones” in the freepbx, try some of these and see if the phones react to i
<http://127.0.0.1/Bellcore-dr1>
<http://127.0.0.1/Classic-1>
<http://127.0.0.1/Simple-1>
try the above without the htttp://127.0.0.1 , but keep the brackets. Change the ring names with the names you can see in the phone set. configurations. It will be some pocking. Most likely with Ciscos you do not the http://127.0.0.1