RetroArch now has native support for the Bliss-Box 4-Play – a universal game pad adapter – in the latest nightly builds. This support will be included in the upcoming stable release (1.7.0).
RetroArch version 1.7.0 will be released later this week.
For more details, please read our blog article here -
https://www.libretro.com/index.php/bliss-box-4-play-integration-is-here/