As mentioned above, here’s a link to Photopea.
It’s basically PhotoShop in a browser. If you’re used to PhotoShop you’ll find the learning curve is almost flat. For me the hardest part was learning to trust that it would do what I asked - like I expected to have to go through hoops to get files into or out of it, but Open and Close are in the File menu and work exactly as if you were running PhotoShop on your own machine. And the saved files don’t add any kind of watermarks.
PS: It works in browsers on iPads, too. Super handy!