  We consider the 6d (1,0) SCFT on a stack of $N$ M5-branes probing a $\mathbb
C^2/\mathbb Z_2$ singularity. In particular, we study its compactifications to
four dimensions on a smooth genus-$g$ Riemann surface with non-trivial flavor
flux, yielding a family of 4d CFTs. By tracking the M-theory origin of the
global symmetries of the 4d CFTs, we detect the emergence of an accidental
symmetry and the spontaneous symmetry breaking of a $U(1)$ generator. These
effects are visible from geometric considerations and not apparent from the
point of view of the compactification of the 6d field theory. These phenomena
leave an imprint on the 't Hooft anomaly polynomial of the 4d CFTs, which is
obtained from recently developed anomaly inflow methods in M-theory. In the
large-$N$ limit, we identify the gravity dual of the 4d setups to be a class of
smooth $AdS_5$ solutions first discussed by Gauntlett-Martelli-Sparks-Waldram.
Using our anomaly polynomial, we compute the conformal central charge and a
non-Abelian flavor central charge at large $N$, finding agreement with the
holographic predictions.
