The default estimator for 2-level SEM is ML. ML chi-square testing has not been developed for general two-level models, but is available in Mplus for random intercept models (such as V5 UG ex9.6). With random slope models the typical SEM ML chi-square testing for single-level models (testing wrt second-order moments, i.e. means, variances, and covariances) is no longer straightforward and such moments are no longer the sufficient statistics for the analysis.
In Mplus there is also a weighted least squares estimator for random intercept models which for both single-level and two-level data tests the model against second-order moments. This is available also for categorical outcomes.