Many people could. However, the standard assumption is that they were so interspersed in other nations and cultures that any remnant of what they once were was quickly eradicated.
With the exception of one T’shuvah in the Rishonim claiming the Ethiopians are from Shevet Dan, for the most part we assume any “lost tribes” were groups that were disconnected from the Jewish community at some point in Bayis Sheni or later.