PhotoRecull is open source under the MIT License. The code, issues and releases are on GitHub: github.com/mykolad/photo-recull.
Besides the Windows app there’s a command-line version, run with the .NET SDK. It does the same cleanup, one date range at a time, and writes an HTML report to review before anything moves.
The Windows app is WinUI 3 on .NET 10. Builds from source need their own Google OAuth client; the Setup guide covers it. The README has the repository layout and how to run the tests.
Found a bug or have an idea? Open an issue, or email photorecull-support@googlegroups.com.