What if the country I'm going to does not support eSIM?

If you intend to use it in the USA most often, get a roaming plan from an USA carrier.

If you intend to use it in the other country most often, buy it from a store there.

You'll likely be denied warranty service outside the country of origin.

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Understand that “eSIM Support” only refers to the ability of the local carrier to PROVISION an eSIM for one of their own users.

An eSIM will work and roam on a network ANYWHERE a nanoSIM from the same carrier would work.

You would need to purchase a model outside the US, preferably in the country where it will be used.

See information in Use eSIM while traveling internationally with your iPhone - Apple Support