-E<source> will adopt orphan dependencies with links to their man pages online, with -Eposix, -Elinux, and -Efreebsd built-in, and -E<path> using a user-specified text file mapping symbol names to URLs.
For
-E posix, https://pubs.opengroup.org/onlinepubs/9699919799.2018edition/idx/functions.html could be used to generate the symbol mapping.