Sorry, but that’s not likely to be developed anytime soon (if ever).
Consider the following:

According to WP counts , don’t think this is necessarily too accurate , but as a rough guide:

– https://wordpress.org/plugins/search/woocommerce/
5+ million installations

– https://wordpress.org/plugins/search/stripe/
1+ million installations for woocommerce
(i.e 20% )

– https://wordpress.org/plugins/search/sumup/
10k (generous) installations for woocommerce
(i.e 0.2% )

===================

– https://wordpress.org/plugins/search/wppizza/
1,000+ active installations

So WPPizza SumUp sales would be something around 2
I cannot see any ROI here even if I were to hike gateway prices by 100%+ and/or sales would be 10 times that

From past experience: I have developed several gateways for wppizza (https://www.wp-pizza.com/gateways/) . Many based on someone asking for them – just like you are .
As it turns out , the development of some of them was a complete waste of time (one person even asked for the development of one of them without ever even buying it when it was completed).

So, as it stands, I cannot see myself adding any gateways to the ones that already exist until there’s some sort of quantifiable demand for a new/additional one that would make the effort worthwhile instead of spending time on something more useful to more people.

That said, if you or someone else wants to develop such a thing , there is of course the skeleton gateway in the add-ons dirctory of the wppizza plugin or – indeed- if someone can present convincing numbers I’d be happy to look at such a development of course.

PS: It is of course not only about the raw numbers of individual gateway sales as the offer of a particular payment option may make people buy into the whole wppizza ecosystem including all the other add-ons.
However, from what I can see, the penetration of sumup in the wordpress space is just not there (yet)

….. happy to discuss though . Maybe I’m missing something …..