OpenBSD has a help command that’s basically just an alias for man, except without arguments it opens the manpage for help(1)¹. GNU help is a bash builtin for help with bash builtins, but does redirect to more general help.

  GNU bash, version 5.0.17(1)-release (x86_64-pc-linux-gnu)
  These shell commands are defined internally.  Type `help' to see this list.
  Type `help name' to find out more about the function `name'.
  Use `info bash' to find out more about the shell in general.
  Use `man -k' or `info' to find out more about commands not in this list.

¹https://man.openbsd.org/help