forum.hardware.fr is a big one (it's not just about computer hardware, there's a decent section about news/world events, etc.)
What I assume is the equivalent, forum.hardware.no, used to be huge in Norway in the 00s too, but then the community more or less got swallowed by Reddit. Did the French one survive?
The real interesting thing is that there are a lot of threads for very specialized topics (e.g. bikes, mattress, pizza oven or torch lights). Before buying something I usually check if a thread exists and read it / ask questions. You however end up having to revise upwards your budget to buy the stuff they recommend.
is a 20 years old French audio/music gear website featuring an exhaustive product database, reviews, newsletters, forum, social network, and marketplace.
Most musicians / producers in the country will be aware of it, including probably some famous ones.
I don't know of an equivalent in the Anglosphere (gearslutz.com would be the closest thing in terms of forum/community, but lacks most of the other features).
Audiofanzine does have some English content, but I don't think that ever really caught on.
Around 2005 there was a very cute php generalist forum called kopikol.net but I still lament that they had to close around 2008