Three UK is not an option - requires UK Credit Card for Top ups. Same with Google Fi (US Credit Card).
With Revolut maybe? just saying
Sure, not all countries are equal, but most Western countries have good rates. You found an example of a closed country that happen to sell prepaid SIM cards to foreigners and where the rates appear to be lower than DrimSim (after you use ~120 Mb). If I need to travel to such a country for a few days, I would think twice if I should figure out how to buy a SIM card and surrender my personal information to them, or just ration my internet use.
I could successfully top up my UK Three card with a non-UK payment card through www.ding.com.
A GBP 10.00 top-up cost me CHF 15.83, including CHF 1.34 “processing fee”. On top of that, they must have hidden a (relatively) hefty “currency conversion” surcharge, which I’m well aware of. For instance, today’s rate would be CHF 14.99 for GBP 10.
However, the convenience was well worth it. And I was able to use the add-on internet allowance in one of their “Go Roam” destinations in South America - so it was still a huge bargain compared to anything from the Swiss carriers (Three had 4GB of roaming, whereas with my Swiss Sunrise subscription I would have paid 79.90 for 2GB in the same country).
… I’m happy with three (UK) as well! Although I’m not going through the hassle of ordering directly from three or topping up a SIM-Card.
I order my preloaded / registered (whatever) SIM-Cards from here: https://www.mymemory.co.uk/3-payg-4g-trio-data-sim-pack-with-12gb-data.html
You get 12 GB of data roaming withing Europe (any some other countries) for 27.99£ (+2.95£ shipping to CH), and: the data lasts for 12 month!
… had no problems so far (used 5+ SIM-Cards)