Hmm, I don't use the mod-pack so not sure if that might cause it, though I can't really imagine what it'd do that would only interfere with the background removal.
When you say it all turns white, do you mean that it's just an entirely white image, or that it's just the background that turns completely white, while the character is still visible?
I tried using the same SD model here but it works fine for me, what other settings do you have when it comes to sampler, steps, cfg scale, denoising strength and resolution? Are img2img, upscaling and ADetailer turned on or off?
If you try to enable the ABG Remover script in web-ui when generating an image there, do you get the same result or does the transparency work there?