Hello, thank you for reaching out to Microsoft Q&A.
May I know if you are currently part of the Windows Insider Program?
The KB5065789 update you mentioned is a preview update that was released through the Release Preview Channel, which is typically available only to Windows Insider members.
If you are in a release preview channel, go to https://www.microsoft.com/en-us/windowsinsider/ and download the latest ISO file available for your channel.
For e.g., Windows Release Preview Channel -latest build in Windows 11 and download the 25H2 ISO file.
Once downloaded, Mount the ISO file and run the Setup.exe to begin the installation.
Make sure you back up your files before proceeding with the upgrade process.
Let me know if you still need more help.