hiss on quiet line is not normal - with cordless dull hum is often heard so have you tried using the test socket with filter to make sure problem is not caused by your internal wiring or faulty faceplate
have you had problems with connection dropping or just many reset as engineer tried to fix your conenction? it looks like all the drops/resets have resulted in DLM seeing your line as unstable an put you in a banded profile
I’ve a brand new socket on the wall and no internal wiring for extensions, just a brand new openreach socket straight to new grey BT test box on wall outside .
No other wiring in the house and all brand new from BT manhole?
It’s a mystery
I’ve a raspberry pi on short LAN next to the hub, a Blink server and a LAN over mains adapter, the Pi has always been there, the most recent is the LAN adapter and Blink ?
If you are dropping internet connection on a daily basis then not surprised you are in banded profile and you will not get out banding until connection problem fixed
Just reading and was curious. Does the hiss disappear when you unplug the nearby devices - LAN adapter and Blink box and perhaps the Pi too - from the mains socket? Unlikely, but perhaps worth a try to eliminate possible sources.