This happened with one of the updates to the PCSX Rearmed core, I noticed it too. Seems like anything with dualshock support is broken at the moment. Happened to me on Switch and Android, ended up having to find an older version of Retroarch to get it working again. I have no idea where to...
It's very good for about half the games in the library in my testing. Anything 3D is hit or miss, I feel like once the other major updates to MelonDS hit the switch core then we will really see fantastic Retroarch DS support on switch. For now the standalone outperforms it.
Amazing work on this! Thank you for doing it, sooo many more games are playable now :)
Is it possible to add the space-between-screens functionality to the libretro core? It works great in the standalone but I don't see it as an option in the core, thanks again!