I recently switched back to using Ubuntu as my desktop OS, and was intrigued to see that Photopea was the default app to open many file types, including PDF.
I thought that was odd because while Photopea is free-of-charge, it's not completely open source [1].
If you’re happy with the feature set of ~Photoshop CS2 you may want to check out Photopea [0]. It runs in your browser, has a similar UI to Photoshop and (for me) has all bells an whistles. It’s also open source [1].
Photopea is not open source [1], it is a free SaaS. Photopea's Github repository [2] is only for bug tracking apparently.
[1] https://github.com/photopea/photopea/issues/45#issuecomment-...