AI responded to the question of the source in Ramban

 Conclusion

While Ramban does not explicitly comment on mamzerim in the Messianic era within his Torah commentary, his broader teachings about redemption, divine justice, and societal rectification strongly suggest that such issues will be resolved. His focus on purification and universal perfection aligns with the Talmudic view that lineage issues will cease to exist during the Messianic age.

3. Universal Perfection in the Messianic Era: Ramban's commentary on Genesis 49:10, regarding the prophecy of Judah and the coming of Shiloh (the Messiah), emphasizes the universal perfection of the Messianic era. He sees this time as one in which all imperfections will be rectified, and the world will return to its ideal state as intended at creation. This would likely include resolving the status of mamzerim, as part of the general healing of societal and halachic challenges.