On thing that hasn’t come up is looking at posterior pair plots. This is my first step when diagnosing divergences. I’m looking for 1) high pairwise correlations (plots that look like straight lines), and 2) clusters of divergences in the parameter space. If a cluster is at a boundary (like a truncation point) this is an obvious problem. If it’s somewhere else, it might indicate something higher dimensional.
I recommend this article by Michael Betancourt about diagnosing pathologies for a deep dive into this issue. Not much in the way of how to resolve it, but knowing how problems come about is still extremely helpful.