Genesys Cloud - Main

Is there any way to enable ringback on internal calls?

What language do you have set on the SIP Phone Trunk?

I hear ringback on my production organization for internal calls, so I am wondering if perhaps there is something configured differently on your trunks.

Portuguese - Brazil (pt-BR), in your environment are you using which one?

I tried en-US and en-GB, and those had ringback, but when I tried pt-BR there was no ringback.

I think you should contact Support and submit a bug report...it should default to en-US if nothing else.