>Can you point us, or perhaps just me, to something that explains that and which countries this applies to?

Gladly https://www.efginternational.com/us/insights/2021/gold-and-b...

>I think that I'd have a hard time paying the Norwegian tax authorities with gold or silver.

This might be even true since Norway is not in EU but I would be surprised if Norwegian banking had been that different from Basel system.