After upgrading to ITMS 8.7.1 you noticed that the iPXE web app was not created.
ITMS 8.7.1
This issue seems to occur on a Site Server that do not have .NET 4.8 installed
You need to make sure .NET 4.8 is installed and NBS service is present by doing the following:
msiexec.exe /x "Symantec_DeploymentSolutionSBS_8_7_x64.msi"
msiexec.exe /i "Symantec_DeploymentSolutionSBS_8_7_x64.msi" /l*v sbsInstall.log skipaim=1 REBOOT=ReallySuppress