esim card for switzerland, italy and Austria for 15 days (only need data plan)

I think you're slightly barking up the wrong tree....

What matters is how much data usage you buy, so you need to have some idea of
how much you expect to use; e.g., will you use it just for nav and limited email/
data needs, or will you stream movies in 4k in your hotel room at night?

If it's the latter, there might be more to discuss. But an Airolo 5gb esim for Europe
for 15 days is $19. I don't see a whole lot to be gained from trying to cost-optimize
that.

All eSim's are used in more or less the same way. How that works depends on your
phone as much as the eSim.

Try this eSIM data plan from Airalo for Europe region.

https://www.airalo.com/europe-esim

I used Roamless which is a pay-as-you-go plan good for most countries including your list. In most European countries, Roamless charges about USD$1.95 per 1GB of flex data.

Roamless may still have a free promotion for ROAM25, ROAM50 and ROAM75 which provides three buckets of free 3 GB each in about 75 countries.

My wife and I were able to use Roamless for 3 weeks in Germany, Czech Republic, Austria, Slovakia and Hungary without too much problems. In the end, when the free promo data finally ran out, I only spent USD$1.75 in flex credit data. My unused credit balance is not lost and is saved for a future trip. This is much cheaper than buying a USD$20-30 30-day block of data which expires if not used.

Another thing that I like about Roamless is that I am able to make telephone calls from the app. This is very useful for contacting hotels or vendors by telephone as necessary.

Hi funpig! I'll jump in and agree with everything you said. Roamless works great for me. I really like the Pay As You Go concept, I pay no monthly fee, and my account balance never expires. I just pay $ 2.45/Gb for most countries. And the phone calls using their app cost about 5 cents/minute, I think. And it continues to work here in the US for my backup phone for $ 1.95/Gb.

So glad that I came back to revisit this post. I just installed the Roamless app and it worked really well right here in the US.. This means I can just use Roamless instead of my current Google Fi for data roaming while at home, as it's only $1.95/GB for US, which is much cheaper than Google Fi's $10/GB. And I really like the idea that the paid credits have no expiration data. I will continue to use Google Fi for my primary phone line.