Security checks and money belts

I'm assuming you're referring to Airport security?

Body scanners will of course detect money belts and neck pouches.

Metal detectors will likely catch them if they are RFID lined, or contain cards in RFID sleeves.

Just zip them into your carry on before going through security, then put them on (find the closest bathroom) once you're through.

Keep them in your personal item bag until you are about to deplane at your destination. You are not going to mugged or pickpocketed in the airport. You are not going to be mugged or pickpocketed in 99% of Europe, anyway.

Sorry, no: I'm wondering about the museum and event security checks.

The only metal on Rick's versions of these items are very tiny zipper pulls. So you would only worry about pat-downs or full-body scanners, neither of which would be expected in museums. (If something else on your person triggers an alarm at an airport metal detector, then it may turn into a pat-down.)

I have only encountered rigorous airport-style security at the many museums I visited in Paris last year (and the Eiffel tower), and my belt-loop pouch was not of interest to them, they just checked bags. At the airport the pouch goes on after security, but otherwise I just wore it as usual.

If the events are at a presidential palace or an embassy then the security might be pretty picky about checking you out,
but otherwise probably not. I'm thinking of spots like the British ambassador's residence or the Palazzo Quirinale in Rome
which are both great places to visit but maybe not on the radar of a first-time visitor.

Thanks so much for the answers!