Technology

I was in Japan 1 week ago. I couldn't get roaming to work with my carrier mint (which may not have been there fault, it's a long story) but I needed data or I would have no way to navigate Tokyo. I paid $25 for 14 days of unlimited 4G data in all of Japan, I downloaded an esim, boom now I have data on my phone again. Easy.

I did all of this on free airport WiFi.

And once u have a sim on ur phone u can switch which sims you have active at a givin time, which had no value to me, but could be useful for other, especially someone who may travel frequently.

There is better: eSIM that let you buy cheap data anywhere in the world.

Revolut offers one, also ubigi which is even cheaper.

This way you don't even need to find out which operator to use in which country.

Well, this is a bit tricky to answer:

1. The e-sim in a phone is a separate chip with proprietary firmware. The chances of a FOSS version of this HW are nearly nonexistent. It would require developing your own silicon and putting it into your own phones. Chances of FOSS FW for this proprietary HW are also very small, because it is difficult and there is not much reason to do so.
2. Currently, registering an e-sim requires a proprietary app (usually google). There is no FOSS alternative. Work on one is slow and there are some IP issues.
3. Using an e-sim does not require a proprietary app. So you can remove google services or remove their access to the e-sim HW once you have it registered. GrapheneOS uses this.

What exactly is the great advantage of eSIMs if you have a dual SIM phone?!

They are slowly phasing our sim card slots, my phone only has one sim card slot + eSIM. Without the eSIM, I'd be force to change or buy a new phone.

What exactly is the great advantage of eSIMs if you have a dual SIM phone?!

eSim means you don’t have to go to a store to get a physical SIM. You can use a ‘SIM store’ app to get an eSIM for wherever you are.

Another minor advantage is that you don’t need a SIM PIN as the SIM is a physical part of the phone. So you only need to enter one code when you restart your phone.

In some countries it’s not easy like walking in to a store and getting a prepaid card. You need to have an ID and a local address, probably to prevent bad events which use sims cards. A travel sim could be easier but more expensive.

eSIM is much easier and can be activated using an app.

What exactly is the great advantage of eSIMs if you have a dual SIM phone?!

If the phone supports a normal and eSIM at the same time, they are equivalent. Because in many countries, dual SIM phones are (and will be) harder to get than single SIM ones, so having eSIM at least allows that.