Although the ctags manual page for a typical Linux machine says that that the -R
switch can be used to generate a "tags" file recursively, the manual page for OpenBSD does not mention how to achieve this. So how do I do this on OpenBSD? Am I missing something? Please help.
I am using Vim 8.0.987
The former is "Exuberant Ctags", the latter is "ctags". They are different programs so you can't really expect them to have the same options/features.
If you want Exuberant Ctags, install it.