Does Painter 2020 save a PNG file in 24 bit format.
Save one as PNG then check it's Properties to see if 8 bit or 24. Corel Paintshop Pro has a PNG Optimizer but I don't see anything in Painter.
Checked the Detail folder and it states 32 bit Depth. I wonder if this is a 24 bit with Alpha channel.
Well, PNG is supposed to preserve transparency, so I assume it has alpha channel- try it out on an image and see.