Are the Donmeh, the followers of Sabbatai Zvi that took on Islam but practised some Jewish laws in secret, considered Jewish at att or would they require a full conversio to be considered Jewish?

Shalom Marc, The Donmeh have been removed from the Jewish community for many generations, and have often intermarried and assimilated with non-Jews (including many who’s spouses underwent non-kosher conversion). This need for them to undergo a full conversion is also clearly in their interest as well, especially those followed their custom of taking each other’s wife, where if they were Jewish, their offspring would be considered mamzerim (bastards) and wouldn’t be allowed to marry Jews. But as gentiles, requiring full conversion, they are allowed to marry Jews. With Love of Israel, Rav Ari Shvat