Meta-analysis of multiple outcomes and multiple treatments: Stan/brms code example?

I want to fit a Bayesian meta-analysis of multiple outcomes (multivariate) and multiple treatments (network) model, as explained here by Riley et al..

Unfortunately, I cannot find any R package to fit such a model (can only find either only network or only multivariate). Thus I would like to switch and use a custom Stan or brms code.

Has anyone fit this model with Stan or brms? Any code would be of great help.