I got this to work today on my macbook pro. MacOSX security was not allowing the app to launch. The app had no code signature at all, and macOS 26 on Apple Silicon kills unsigned x86_64 binaries outright when Rosetta tries to translate them (SIGKILL — Code Signature Invalid). I applied a local ad-hoc signature with codesign --force --deep --sign - "Pixel FX Designer.app", which satisfies that check without needing a real Apple Developer certificate.