Serif’s Affinity Photo is currently the king of the "buy it once" model. It costs roughly $70 (often on sale for $40). It is faster, modern (supports 4K screens and GPU acceleration), and reads/writes PSD files. If you loved CS6 because you hate subscriptions, this is your new home.
Have you successfully installed CS6 recently? Or did you move to a newer tool? Let me know in the comments below. photoshop ps6 download
Go to Photopea.com. It is a browser-based app that mimics Photoshop CS6 almost exactly. It opens PSD files, uses the same shortcuts (Ctrl+Alt+Z for undo), and supports layers. It is free (with ads) or cheap for premium. For 90% of CS6 users, this is the perfect replacement. Serif’s Affinity Photo is currently the king of