eSim on iphone 8 plus

The cellular / mobile service provider (carrier), needs to support the eSim activation as well.

Zanzibar does not appear to have any carriers that support eSim at this time, so you would not be able to use it, even if you had an iPhone that had it.

See here: Find wireless carriers that offer eSIM service - Apple Support

Why do you think you need it again?

In addition to Phil0124 excellent comment, is there a carrier available in your area that is capable of supporting them?

eSim is not available in an iPhone 8 plus. It lacks the hardware for it.

You can't magically add a eSim to the iPhone 8.