Father & King Marrying Gentile - followup

Dear Rabbi, This is a follow-up question to an answer given on 18 Shevat 5765 regarding "Father & King Marrying Gentile". In the answer it was said "Your question is dealt by the Talmud itself in tractate Yevamot 76a and the Talmud states that King Shlomo converted the daughter of Pharaoh when he wed her. Same to all those that married "out" – the wife was always first converted. There is a difference between the process of conversion before Matan Torah and after, yet, no non - Jewish girl entered the righteous Jewish families." Could I ask for clarification regarding Ruth an ancestor of King David please as the last remark was that no non-Jewish girl entered the righteous Jewish families. When Ruth married Boaz, though she was born a Moabite was she already considered to be Jewish because she was the widow of Naomi’s son? Would she have converted to marry Naomi’s son already or did she convert to marry Boaz? If having converted, Ruth would now be Jewish correct, so is that why you say no non-Jewish girl entered the righteous Jewish families?

Boaz married a Jewish girl; when she gave birth to King David's grandfather, she was Jewish. When Naomi's son married Naomi it seems she was not yet converted [and this is the way Rashi and others understand]. This puts Naomi's son in bad light, but on a simple note he wasn't a "righteous Jew". The Ibn Ezra, on the other hand, holds based on our sages that her son's were righteous Jews and he understands that she was converted [to a certain degree] for the marriage with her sons.