You can output to a plain background and use any number of tools to mask it.

I know. It sounds like a perfect task for AI to do it though (wasn't the whole premise of AI do to mundane things for us), yet they fail to do it, and I need to use an external tool.

	▲	minimaxir 3 hours ago \| parent [-]
		Alpha is a 4th image channel that 99%+ of images in the training data do not use, so it makes more pragmatic sense to just not allow it.