The power cable on a PC power supply unit is plugged in. If you have another one from another device that fits, you can use that too.

However, you can still complain to Digitec Support and have a correct cable sent to you. see below

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Digitec is obliged to supply electrical appliances with a Swiss plug. If the appliance has a foreign plug, a suitable replacement cable should be supplied if the mains cable is pluggable or, alternatively, a suitable adapter if the mains cable is permanently connected.

If the appliance is delivered without a suitable plug, complain to the customer service and insist on a cable or an adapter, free of charge.

Point 1 --> https://www.esti.admin.ch/de...

No, there are no restrictions. If there were, it would have to be noted on the cable.

If you look closely at the plug on the power cable that goes into the power supply unit, you will find the inscription "10A 250V". This is what the cable is specified for. This is more than is needed for your power supply.