Studio ML removers are excellent and expensive to host, which is why they meter credits. Our Background Remover is a corner flood-fill: it treats the color at the edges as the backdrop and punches it to transparency.
That is the right algorithm for product shots on white, ID photos on a wall, and stickers. It is the wrong algorithm for windblown hair on a hillside.
Threshold up if bits of backdrop remain; down if the subject is being eaten. Download a PNG, then drop it on Passport Photo Maker if you need a solid color behind a person.