I read another past about the same topic, and one of the comments was that a sprite was allowed inside an image. I think that answer was incomplete. It seems to be possible, but a little more complicated than that.
In this forum the selected answer gave an option that worked for me. I changed the canvas ‘renderer mode’ to be “Screen space - camera”, and then selected the main camera. After that sprites worked as expected for me. https://answers.unity.com/questions/835737/gameobjects-added-to-canvas-do-not-show-in-game.html