On a fairly minimal system (one of our jumphosts) I had screen installed by our provisioning system but "man screen" told me I needed to install groff. Looking through other ports-related bugs, I found this related issue for bash: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=234992 So either screen needs to process its man pages in such a way as well, or groff should be listed as a screen dependency.