It's going back ten years now, but after a truly rotten, wet & windy day my better half & I decided that the last thirty miles of our day would be best spent in the comfort of a train carriage rather than enjoying the feeling of rain running down your legs and into your shoes, so we abandoned at a local train station somewhere near Bayeux (as in Tapestry) and caught the train. Two Brits, a fully loaded Dawes Galaxy Twin, an English / French phrase book and no idea what to expect.
It could not have been easier. The ticket machine had an English option, the station staff helpful, the train a large bicycle symbol and as mentioned up thread the train itself had loads of hooks to hold solos vertically. We couldn’t use those hooks and I ended up just tying the bike to a vertical grab rail, not perfect but nobody battered an eye lid or raised an under the breath grumble or otherwise.
Now, it might have been the case the station staff saw two thick Brits with a loaded & oversize bike and realised that we would cause their train to run late if we were slow at loading up and maybe they were just being helpful to avoid any delays. No ideas, but what I can say is that it really was easy and the French local service trains are easy to use.