what guide were you following that told you to install coturn for Element X? It shouldn't be /that/ surprising that Element X's group-capable calling requires a group call server, and in general most people seem happy to not have to worry about coturn given the server acts as a relay.
Element (not ElementX), the official/preferred app, works with coturn for 1-on-1 calls. But ElementX does not. IMO it is surprising to break 1-on-1 call functionality.
In Matrix 2.0, all calls are group capable (much like Matrix itself doesn’t specialcase DMs - they are just rooms with 2 people). So yes, no coturn is needed.
We haven’t got as far as interop between legacy Matrix 1:1 calling and Matrix 2.0 style MatrixRTC though, which I can see being annoying - but overall the admin burden should be simpler than running a coturn.
We’ll update the synapse docs to explain that coturn isn’t needed for MatrixRTC calls.
