How to add FCEUnext core?

[matchaman]

I'm looking for a way to use FCEUnext instead of Nestopia.

Kid Dracula refuses to run on Nestopia (it's a known issue), therefore FCEUnext is my only option. This known issue is also present in several Japanese titles, especially when it comes to Konami.

I don't understand why only Nestopia shows up, while Recalbox's wiki contains details on so many libretro cores. Generally speaking, FCEUnext is a better core.

https://wiki.recalbox.com/en/emulators/consoles/nintendo-entertainment-system/libretro-fceunext

[matchaman]

Please note that I tried configuration override as instructed:

https://wiki.recalbox.com/en/advanced-usage/configuration-override

And also made sure that the core is present at /usr/lib/libretro

It seems like Recalbox completely ignores my overrides.