Hi, i want to know if in karma it's possible to work in aces also with backplates footage usidng the new node backgroundPlate

Are you asking because you've tried it and it's not working as you expect?

I haven't used it - but would bet 50c that it works.

Ensure you've an OCIO configuration, and that it's being pointed to by the OCIO env var. An internet search for "houdini ocio" gives a couple of good videos showing you the setup and the techniques for ensuring you're managing your colour space for plates and textures.