Sorry, the only gateways currently available are the ones listed here:
https://www.wp-pizza.com/gateways/

Although there will be more in due course, I cannot tell you which one will be available and when as it really depends on the popularity of a particular gateway as to whether or not there is worth spending the time in reading/understanding the documentation, programming and testing things etc. to develop it .

At the moment at least , this does not seem to be the case with “SumUp” I’m afraid (though this might change in the future of course).

That said, if you are desperate, there is a skeleton gateway available in the “/add-ons/” directory of the wppizza plugin you could use to develop your own based on your chosen gateways API