Hi,
I modified ep128emu a bit to be able to work as a libretro core, with RetroArch frontend. Most things seem to work, and a few convenience items are also added like content autostart (where possible).

Find it here: https://github.com/zoltanvb/ep128emu-core/releases/tag/core_v0.7 . Currently Linux and ARM versions are downloadable.

Comments welcome!

v0.85 is out, with smaller improvements:
https://github.com/zoltanvb/ep128emu-core/releases/tag/core_v0.85

v0.90 is out, with smaller improvements mostly related to configuration options.
https://github.com/zoltanvb/ep128emu-core/releases/tag/core_v0.90

v0.93 is available, small improvements like speaker state control.
https://github.com/zoltanvb/ep128emu-core/releases/tag/core_v0.93