1 year warranty, pretty good considering what you usually get. They accept payment with crypto not bad either.
How does it work for PSU (you can use server ones, what about ATX ones ?) ? how do you "start" the system ?
You can use both server PSU or ATX. The board itself does not have an ATX 24 pin connector, it is powered by 2X regular 6 PIN connectors, the same kind that you power your GPU and all the mining PSUs use. The motherboard automatically start once power is connected. So you can start it just by switching the PSU on. You can change those settings from the BIOS if you want and you can connect a regular computer power switch to it. Both ways OK.