I use the following script to create the transparent PNG. It's not as convenient as having the feature within inpaint-anything, but it works:

#!/usr/bin/python3
import sys

total = len(sys.argv)
cmdargs = str(sys.argv)

if total!=3:
print ("Usage: %s image mask " % sys.argv[0])
sys.exit()

from PIL import Image, ImageOps

load images

#img_org = Image.open('target.png')
#img_mask = Image.open('mask.png')
img_org = Image.open(sys.argv[1])
img_mask = Image.open(sys.argv[2])

convert images

img_org = img_org.convert('RGBA') # or 'RGBA'
img_mask = img_mask.convert('L') # grayscale
img_mask = ImageOps.invert(img_mask)

add alpha channel

img_org.putalpha(img_mask)

save as png which keeps alpha channel

img_org.save('output.png')

from inpaint-anything.

Supported that feature in v1.4.1. It can be accessed by clicking the Get mask as alpha of image button under the Mask only tab. The PNG image will be saved in the folder corresponding to the current date within the outputs directory.

from inpaint-anything.