LDV Pilot van - Squeaking serpentine belt

Chirp! Chirp! Chirp!
My current unresolved problem probably caused by (me)splacement and probably misalignment too which happened I presume when I replaced the belt.
This video from the Dayco videos serie is helping me out.

So far, I took the belt out and re-placed it but to no avail. I noticed a wear on one side, edge of the multi grove belt (referred to as sidewall wear in the video). Some of the worn out rubber seems to have accumulated in and around the alternator too. I cleared it out.
I check manually that all pulleys, discs were sound and to the right tightness. It feels steady but probably needs better checking but no wobble.
I also noticed that on the tensioner roller I can see misalignment of the belt and can't do a thing about it.
My next step will be to take the belt of and listen and I will need to take the brake vacuum pump (shorter) belt to do that.
My guess is that my tensioner is worn someone. Let's see.

Review your belt and pulley basics with Eric the car guy's video and understand why, although it doesn't stop you from using your vehicle, it's not a good thing to use it with a noisy belt for too long as it directly can affect the timing of your engine resulting in more consequent and costly damages to essential parts of the engine like the camshaft itself.

and this is from Chris Fix which I will need in case my "diagnosis" (guess) is correct. That's another belt and tensioner replacement cost.

(Let me transcript this last video bit as it's too fast spoken for me to get it clear)

Diagnosing with water bottle spray

• Run engine (keeps your fingers, limbs, hair, loose clothing away!)
• Spray a little water on the inside rib of the belt (direct to pulley's groves)

If noise stops - the belt is still moving, the pulleys are still moving:

• NOT a bearing problem.

If the noise does NOT change:

• A bad bearing in a pulley

If the noise gets LOUDER:

• Belt tension is too tight or too lose
• which could be due to a bad tensioner pulley
• or could be due to a worn/stretched belt