AFPHOTO file type is the default project file of the Affinity Photo app and not really supported in any other software. Thus the only way how to convert afphoto to tiff or export the projects to another graphics format is only possible with the original software.
Projects are just XML files that contain changes done to original picture, which means you will also need the original picture if you hope to export the picture with the changes, which is what afphoto to tiff conversion represent.
Updated: January 12, 2024