SymBoltz should be able to compute lensed CMB spectra with a few additions. See e.g. https://arxiv.org/pdf/astro-ph/0601594#subsection.3.1 and https://arxiv.org/pdf/1312.2697#subsection.5.5. The calculation seems to be another line-of-sight integration, only with a different source function:

$$ \Delta_l^\phi(k,\tau_0) = \int_{\tau_i}^{\tau_0} d\tau S^\phi(k,τ) j_l(k(\tau_0-\tau)) $$

cc @marcobonici and @sofiachiarenza