Yes, it should stay impossible until right configurations are in place and many users are already running them successfully. You may need to disable the default session helpers, and use ALG instead to start with.
Have finally achieved 2 way audio after months of troubleshooting and re configuration, however can now only dial into Teams, can not make a call out from Teams.
I disabled the SIP ALG as everywhere advised - Been trying to understand VOIP Profiles in case I have something there wrong - Spening nights up at midnight troubleshooting but that call will not connect out from Teams.