While the full OS installer is gone, Microsoft still hosts ISO images containing specific security updates from 2015: October 2015 Security Release 3.4 GB ISO containing security updates released in October 2015. March 2015 Security Release : Security updates for Windows released on March 10, 2015 January 2015 Security Release : Updates for various Windows versions released in early 2015 Third-Party Archives (Full OS ISOs)
Once you have the ISO, you can create a bootable USB drive using: Win 10 2015 iso - Microsoft Q&A windows 10 version 2015 iso
The 2015 build supports DirectX 12 in its earliest form, but not features like ray tracing, mesh shaders, or variable rate shading. While the full OS installer is gone, Microsoft
If you’ve decided to proceed, follow these strict guidelines: but not features like ray tracing