In chelek gimmel of Minchas Asher, on the (first) Teshuva about Matza Rakka the Rav writes that perhaps nowadays we are not able to bake matzos rakkos without chashash chimutz. Does this apply to Sefardi matzos rakkos (that they have a mesorah how to bake them correctly) or just Ashkenazi? Also would an Ashkenazi be allowed to eat Sefardi matzos when eating at a Sefardi’s house?
A Sefardi Jew who has a family tradition to make such Matzos and how to do so, may rely on his family tradition.
An Ashkenazi should avoid such Matzos even when at the home of a Sefardi. See there Siman 45 that on cases of absolute necessity there is room for leniency for an Ashkenazi.