Bedrockgames
I post in the voice of Christopher Walken
The issues with Conan are not that cut and dried.
The last of REH's released-in-his-lifetime works are not in the public domain in the US. The copyrights were extended, so, being post Steamboat willy, it's life + 95 years. He died in 1936, so.. 1941... 2031. 7 more years for the last of them. (Note that Australia has a shorter copuyright term, so many things are on Gutenberg.net.au that are not yet on gutenberg.org. Including certain Howard and Borroughs works.)
But Howard actually isn't the most prolific of the Conan authors. Lin Carter, L. Sprague deCamp, Donald M. Grant, and others have written as much or more each, and those works are all still in copyright.
The estate, I don't know if it's a corporate entity, or just IP ownership, also owns the Trademarks.
I guess the trademark would be quite a hurdle. How would that work though if a story itself enters the public domain but has Conan in the title ?