Just to clarify, in case anybody is still confused.
The signs for the Brecon Beacons have always had Bannau Brycheiniog on the sign as well, it’s not a new name, just that the national park is now to be known by the Welsh name not the English version.
Pen y Fan is still a beacon, it was last lit for the Queens Jubilee last year - there are quite a few in this area which is probably why it became known as the Beacons originally. King Charles has decided that the beacons won’t be lit for the coronation because he wanted it scaled down.
Brecon town is called Aberhonddu in Welsh, with Breichiniog being the medieval name for the kingdom of South Wales.
Pen y Fan is the highest peak of the Beacons, and is not the same mountain as Sugar Loaf, which is near Abergavenny, about 20 miles from Pen y Fan, but still within Bannau Breichiniog. Sugar Loaf is also a beacon.