The present study takes a variationist perspective to explore the varietal repertoires of adult learners of German as a second language (L2), that is, their variable use of standard German, Austro-Bavarian dialect, and mixture varieties. Forty L2 learners completed a virtual reality task involving interactions with dialect-speaking and standard-German-speaking interlocutors. Using Bayesian multilevel modeling, the goal was to explore differential outcomes in the acquisition of sociolinguistic competence by determining whether participants adjusted their varietal behavior to match that of the interlocutor (i.e., varietal convergence). The results show that there were no interindividual addressee-dependent convergence tendencies. A holistic person-centered analysis of individual learners' intraspeaker variation revealed that only select L2 learners adjusted their usage patterns but did not entirely invert their usage of dialect and standard language as a function of the variety of the interlocutor. Introspective qualitative data speak to potential drivers behind the differential development of L2 (multi)varietal repertoires.