Windows 11 Insider 26220.9587 keeps reinstalling

Hi, I need some help with Windows 11 Insider Beta.
I'm currently on Windows 11 Home Insider Preview build 26220.9587. The build installed successfully, but Windows Update keeps offering the same 26220.9587 feature update again and later attempts fail with error 0x80246019.
I also have the “Evaluation copy” watermark even though Windows is permanently activated.
I have enabled the option to unenroll my device from Insider builds. My goal is to return to stable Windows 11 without resetting the PC, deleting my applications/files, or doing a clean installation.
What is the safest supported way to do this?