Photoshop, GIMP, Affinity Photo, and Photopea all support transparent PNG export. So do browser tools like Remova, which removes the background and exports the transparent PNG directly.
The easiest path is to use a background removal tool that outputs PNG with transparency built in. That removes the need for manual masking and export settings. You upload an image, the tool does the work, and you download a file that is ready to use.
If you are working with an existing transparent PNG and want to verify it, open it in a browser or editor that shows a checkerboard pattern behind transparent areas. If you see a checkerboard, the transparency is real.