I am looking for an R package that can fit ordinal responses with a mixed model (so random and fixed effects), including genetic relationship matrices.

Packages that I have looked at include R-asreml (allows some generalised linear model families but not ordinal), sommer, and more recently the welcome lme4breeding package. The latter also allows for different families but I don’t think these include multinomial distributions for ordinal responses. I don’t think clmm will fit random effects with the variance structures needed.