I tried and then as expected the Xfce clock was on time but the system time was wrong (showing the UTC time but telling it was CET). It didn't solve the TLS problem. I think the problem comes from the difference between these two clocks (just why is Xfce adding +1:00?), but maybe it's something else. I'm going to investigate this next week.
Don't waste too much of your free time for me, this is not a priority 🙂
As for now I'm just exploring NetBSD. If everything I need turns out to be possible with it I may consider using it more seriously.