Pulleys are correct orientation and correct order.

Can you verify that's actually an 11 sp chain?
You have 11 gears on the cassette, right?
In one of your photos the chain looks all scratched and worn on the side of the chain.

Pretty sure it's 11 speed but as I said before, tempting to buy a genuine 105 11 speed chain. This came with the bike and should be KMC 11 speed.

Also yes, some dry lube on the chain flaking off. Using Squirt.

Are your dropouts bent? The wheels centered?

Wheel is centred. Dropouts straight.

https://cimg2.ibsrv.net/gimg/bikefor...3df1a0cdf1.jpg
I'm not a chain expert, but I see an 8c stamped on the chain plate. That would make me think it was an eight speed chain and would explain the noise. But if you didn't change the chain and it just started making that racket, I would try a new chain.

Its not really 105. Its a KMC chain. How about the casssette? Is that a Shimano or something else?

I would get an other chain cn hg601 and make sure its a proper Shimano cassette.

As I said earlier I think, chain is on my to do list.
It's gone back to my LBS today, fed up!

I'll let you know how it turns out

So what was the problem? Operator Error?

Ha! Nice!

It's still at the shop. They've not solved it either but thanks for your vote of confidence.

I did route a chain through the rear derailleur wrong once. Rode it quite a ways that way until I realized what I had done.

For this problem, my vote would be chain. i.e. not 11 speed chain.

bent rear derailleur hanger?

+1 on the bent derailleur hanger.

So Now you want quiet ? get a belt drive single speed ... gates carbon drive , that will be quiet.

https://www.gatescarbondrive.com/pro...-freewheel-cdx

https://www.gatescarbondrive.com/~/m...rbon-drive.jpg

I seriously doubt the OP is going to go through the hassle of going to a frame builder to have a gate installed in the seat stay over a bit of new drivetrain noise.

Maybe it would be a good time to install S&S couplings, new Paragon sliding disc dropouts & a pump peg while he's at it?

Both the chain and cluster look like they have been grinding away. Only the 11T looks shiny.
I have to agree it must be an 8 speed chain. You def need to replace both chain and cassette.
The first time I changed my chain on the Rohloff, it sounded like I was dragging a tin can. The front teeth were gouged.

Could it be because the chain is too thick? Ie, grinding against the adjacent cogs?

Amazing isnt it. The forums are littered with threads like this. Seemingly simple issues that no one seem capable of solving.

This!
From the visible wear on the link cheeks, it has to be that the chain is too wide - Or, it's horribly cross-chained
Probably should change out the cassette also, if it's been grinding away like that, all this time.

We will never know.....'cause the bikes in the shop.

You seem fun :)

Yeah - the bike is in the shop. The lacquer was peeling on the dropouts too so it's gone back to Ridley under warranty.

Shop also found that the hanger was slightly out of alignment. So - we wait for it to come back with some fresh paint and a straight hanger and let's see how it goes!

The points on chain have been noted, it is definitely the right sized chain for the set. I'm going to swap it for Shimano anyway just so there' no doubt over any mismatch going forward. KMC 11 speed should fit though...

Nice. Bent hanger. What's with the sending the frame back to Ridley for lacquer peeling on the dropouts? Doesn't that happen anyway?
I guess if happened to my frame I would send it back too....but miniwilly, let's get this bike running for the season! No more excuses!

Don't respond to him.