The Nsight VSE installer for 2026.3.0 is signed by a “NVIDIA DVS Dev Signing” certificate, which chains to a “NVIDIA DVS Dev Root” certificate. That “Dev Root” certificate is signed by a “NVIDIA Dev External 2026” certificate that my workstation doesn’t know anything about (and therefore doesn’t trust).
As a result the installer gets flagged during install.
By contrast, the installer for 2026.2.0 was signed by an “NVIDIA Corporation” certificate issued by Digicert (which my workstation does trust).
Seems like a dev certificate got used for the public release,