^
Nice to see a contribution to this thread. For sure there is good stuff lurking there. I only post what I think is appropriate with good photographs which to be frank is sometimes a miracle in it's self.
Perhaps this won't make you feel much better, but at least a conciliation in a sick kind of way, believe me, even living in France it's an eye candy store too with harsh realities.
Leboncoin made massive changes over the last few years, and pushed them through in the middle of Covid very rushed and bug ridden.
Primarily, Leboncoin was / still is like going to your local Tobacconist and putting a hand written advert on the "local advert board" for many sellers (about 50% at a guess). All the effort is on the buyer and it can be like pulling teeth with seller. It's a nightmare. The new generation during / post Covid embrace the fact that you can do transactions with good security for small things. Leboncoin is in bed with a logistics provider (who just happens to be the most PITA for me) but at least they realised they needed to do something for the small part business.
You now need to have a French telephone number to register on Leboncoin, and even go as far as proving identity and address a bit like Ebay to stop scams. The business model is just 100% domestic France.
I can understand a potential frustration if you like the vintage French stuff, but don't think it's straight forward either domestically - for me it remains the worst purchasing channel and you have to have your wits about you.
I would never do a deal for a vintage bike unless I saw it, and eyeball the seller with a cash deal.
By the way, to be clear, this is not an invitation to being a broker either because even that is now bullet proof.
Sadly for overseas, Ebay is best. There are people who for sure buy on Leboncoin, do some value add, and re-sell internationally for a living.