Lots of shady people on that website...you
might find interesting stuff from time-to-time, but be
very careful.
Google 'matériel broadcast occasion' or 'matériel audiovisuel occasion' and you will find craptons of specialized stores.
However if most of them say they sell used hardware, in reality they're more like rental stores for professionals, so they have very little stock of used stuff, which is usually the stuff they're not renting anymore.
They have close to zero contacts in the consumer world, not the easiest people to talk to.
Anyway, there aren't any pro CRT monitors left anywhere in France, it's really on occasion when people clean up some storage room or get rid of their last CRT's when they're near-death that you will see some appear on the lists.
Then they're snatched by the retrogaming kiddies on eBay (since most stores will have an eBay account) even the most useless totally run-down shit, regardless of the price.