Initially, the local Telcos weren’t doing eSims, so you either had to do the physical sim swap or find a suitable eSIM service provider. They’re all doing eSims now, so one option is to put your primary (local) number on the eSIM and free up the physical slot for local sims you pickup along the way.
*BUT* the advantage of eSims is you can get them before you leave the country or even swap over - without needing to go into s physical store etc.
If your using iPhone, here’s some info:
Find out what an eSIM is, how to set up an eSIM on your iPhone and how to transfer a physical SIM to an eSIM.
support.apple.com
I suspect some people don’t even realise they have a dual sim phone because the esim options in settings don’t appear until you load one.
Click through on the page above shows “eSIM carriers”:
Find out which wireless carriers in your country or region support eSIM.
support.apple.com
If you rock up to one of those countries, you’re supposed to be able to purchase some service and scan a QR code to load up the eSIM.
If you’re just after roaming data, TruePhone, Flexiroam (and others) have packages / bundles. They come with an app to manage the eSIM and packages.