You can always get a Kill-a-watt (or similar if those aren’t available for the EU) to see how much power something uses in standby
I remember there being special power strips you could get to detect and stop phantom loads like this. But according to that article, there are now regulations to keep this power draw low, so it’s probably not a major problem with modern devices.
i have a couple of those power strips at the office. i'm always forgetting about that 'feature' and end up with stuff 'mysteriously' shutting-off or draining battery instead of charging.