Good news. I can finally reproduce the error and will work on a fix later on today.
I fixed at least 2 issues with loo_moment_match that were brms related. Depending on the model you may still need to install loo from github as well to avoid at least one further error.
What is the latest version of LOO? Is it 2.3.1?
Yeah that’s the latest CRAN release. The version on GitHub has a few bug fixes that still need to be released, so it could be advisable to install from GitHub: remotes::install_github("stan-dev/loo").
Ah ok yeah this is what I was wondering. Thank you!