Does the iPhone 8 support eSIM?
No. The iPhone 8 (2017) has no eSIM hardware, so travel eSIMs will not install on it. A physical local SIM or hotspot from a companion device are the alternatives.
Every model in this line from 2018 onwards does support eSIM, so an upgrade brings travel eSIMs with it.
Check it on your phone in ten seconds
Settings, then Cellular (or Mobile Data), then Add eSIM. If that option appears, your iPhone 8 is ready.