Current upstream release is 3.5.3, 3.4.5 dates back to Jun 2021. Poor excuse for restricting tests: # ggplot2 is a test dep but not in portage The only revdep is pandas[doc]. Let's lastrite it?
If you lastrite it, I will adopt it in the sage-on-gentoo overlay. I could look into doing something about the tests.
The latest version (3.5.4) is currently in the tree. https://gitweb.gentoo.org/repo/gentoo.git/commit/dev-python/rpy?id=e934ba01fc6d628ecb6c4ce79b8180badaabe119