Endpoint Upgrade Assistant Package Creator needs a compatible installation package for Trellix Agent, to include in the custom installation package that it generates. You need to download this installation package, called a frame package, from your target ePO - On-prem server.
The correct file is named FramePkg.exe. Files named SmartInstaller.exe or Frminst.exe don't work.
In ePO - On-prem, select System Tree → New Systems.
For How to add systems, select Create and download agent installation package.
For version, select Windows and 5.0.5 or later.
Click OK to download a valid Trellix Agent installation package from your ePO - On-prem server.