This study examines the contemporary phenomenon of the reconfiguration of and identification with Yotvingian (Sudovian) heritage in the Polish-Lithuanian-Belarusian borderland. The constructivist perspective adopted here shifts attention away from questions of the biological continuity of an ethnos and toward an analysis of the social, cultural, and digital mechanisms through which the past functions as a flexible symbolic resource. The paper develops the original concept of post-tribal memory, understood as a form of cultural memory relating to historical communities whose institutional, territorial, and linguistic continuity has been disrupted, yet which remain active as a living repertoire of contemporary identifications. The analysis is grounded in classical theories of collective memory (Halbwachs, Assmann), the concept of sites of memory (Nora), ethnosymbolism (Smith), the theory of imagined communities (Anderson), and critical heritage studies. Particular attention is devoted to the role of digital technologies, commercial genetic genealogy, and large language models (LLMs) in the processes of reconstructing and stabilizing historical narratives on state peripheries. This work was developed in collaboration with generative artificial intelligence tools.