  Recent proposals for the Symmetry Topological Field Theory (SymTFT) of
Maxwell theory admit a 0-form symmetry compatible with the classical
$SL_2(\mathbb{R})$ duality of electromagnetism. We describe how to realize
these automorphisms of the SymTFT in terms of its operators and we detail their
effects on the dynamical theory and its global variants. In the process, we
show that the classical $U(1)$ symmetry, corresponding to the stabilizer of
$SL_2(\mathbb{R})$, can be restored as a non-invertible one, by means of an
infinite series of discrete gauging. This provides an example of the
reemergence of a classical symmetry in the quantum regime, which was not broken
by anomalies, but rather by the quantization of electromagnetic fluxes.
However, this procedure comes at the price of introducing "continuous"
condensates that trivialize all line operators.
