The most famous one is probably PayPal. But I assume for people who are privacy focused, that would be not the first choice.

There is Curve Pay, but I know nothing about it besides the fact that it exists.

Samsung Pay exists, but it only works on Samsung devices and therefore is not really an alternative in this case.

And then there are some regional options. Here in Germany are same banks that offer their own payment apps, most famously the Sparkassen. I heard there are also some Indian and east Asian payment apps, but I don’t know much about them.

Contactless payments does not need to be Google Pay. There are alternatives.