Can you still hear the noise when spinning up a raised rear wheel by hand, might be easier to locate like this.

If you remove the drum again it might be worth applying a touch of coppaslip (with a cotton bud or similar) to the points of contact between slave cylinders/adjusters/shoes and where the shoes rub against the back plate, also check the hold down clips are in good condition.

Recheck the drum for any bright line or slight groove, because of this is something gently touching the drum then it should leave some evidence to help you pinpoint.

I don't think it's the bearing, but worth having a good listen to the bearings by spinning up the hubs with wheel fitted, if you do both sides any difference should be obvious.