OH3: Measurement unit and decimals not displayed for item from remote openHAB binding [SOLVED]

But that is not a Quantity type Item. It has no units, though you can specify a bit of text to be shown in display with it, like %.
You can’t map that to a Number:Dimensionless type Item because its value, its raw state, has no units.
Or rather you can, because Dimensionless is the one Quantity type that accepts a number with no units, but you won’t get the value you expect.