We have decided that Formik and Yup in tandem are currently the best way to handle forms. While there are other good lilbraries, we haven't run into any problems with Formik and Yup that other libraries would fix and we didn't see any compelling reasons why other libraries would be better. Based on that and the fact that we have a lot more experience as a community with Formik and Yup than other libraries Formik was our choice.
React-Hook-Form is an up and coming library that has gained about as much community traction as Formik/Yup. We could see this taking over eventually but currently there is no reason to use it over Formik.