I don’t know what sfardim who make a mizonos on matzah during the year will do This issue was already addressed by Rav Ovadiah Yosef ZTKLLH’H”:- Answwer:- this scenario of Isru Chag Pesach on Shabbos is a unique situation, when the rational that Matzo is your only bread and hence rises from Mezonos to haMotzei during Pesach, is still in effect on this Shabbos Isru Chag, and does not revert back to being Mezonos until after this Shabbos Isru Chag Pesach.
I attended a Shiur by Rav Ovadiah Yosef ZTKLLH’H in person back in the 1980’s when he discussed this question amongst several others.