Does the iPhone 8 have an eSim?
All phones
No. The iPhone 8 cannot install an eSim, so it cannot use Departing.
The iPhone 8 Plus is the same. The first iPhones with an eSim are the XS and the XR.
Check in 10 seconds
Open the phone app and dial *#06#. If you see a number labelled EID, the phone supports eSim.