Construction costs are currently skyrocketing

Corrugated sheet metal and completely covered with photovoltaic panels. Cheaper than tiles, lasts longer, and even generates electricity. By the way, it also works on north-facing roofs. ;-)

Corrugated metal and completely covered with photovoltaics. Cheaper than tiles, lasts longer, and even generates electricity. By the way, it also works on north-facing roofs. ;-)

hm... don't scare me now with the availability.
The carpenter said - no problem. The roof is supposed to be covered in September

Is corrugated sheet metal per se permitted?

If nothing is specified in the development plan, you can build yourself a thatched roof... ;-) If the new building can still be planned and the roof dimensions are under control, I see no reason why one should not opt for a visually not so great solution for the roof waterproofing, especially if the entire rest is fully covered with photovoltaics. In my opinion, that definitely looks better than the usual little bit of tiled roof that sticks out a bit on all sides under the modules.