I have been buying my #train tickets on @12train for a few months now and have been globally happy with the experience. The site is clean, fast, and sufficiently ethical from a surveillance capitalism perspective, which puts them head and shoulders above the competition.
My only issue has been around the proper application of Railcard discounts for accompanying passengers. I usually travel solo so it doesn't come up much, but when I'm travelling with a companion, I still have to use e.g. Trainline. I have raised the issue and hopefully it will get addressed in the future!
Still, top marks and I highly recommend you check out 12train out for all your #TER, #TGV, #Intercités, #Eurostar, and #Lyria ticketing needs.