See if the old decoder still works - I had the same email from Orange though rather more adventure getting the new decoder into my hands as I was not in France when they sent it.
Lazily I did not actually connect it up - but the old decoder was still working so I haven’t bothered (yet).
If your TV is old enough that it only has a SCART input it’s time for a new one anyway 
I suspect the main difference is that the old decoder did not support 4k output (and maybe does not support 4k streams).
As for the standard aerial socket (TNT) - yes, it has a TNT tuner but to be honest I never saw the point of using it as all the channels were in the Orange bundle anyway.