Hi Guenael,
If I correctly see it is a probably first report of this kind of issue with OVH. So it seems that it does not affect such a big part of our userbase.
Anyway at this moment I cannot do to much with this, because the only solution will be changing the FTP library – but we have to be very careful with this so most probably we will release a plugin with a new library (I have some candidates after a research) and if a bigger userbase will test it, then we will replace the basic one.
But it is a topic for Q3 2021 at this moment, because we need to allow Publii to use plugins.