By law in these countries, you cannot use "digital assets" for payment. But no one prevents you from moving the jurisdiction from these countries to a more friendly one for opening this kind of business.

I would be happy to test this, but I don't know how to approach this issue correctly, because I have no experience in this area.

Monotone

bitcoin

How to create a local alternative to Bitrefill?

I am not sure if something like that would be even legal in your country, but maybe there is an option to test this out. Far from being the most efficient/scalable way to run this, but you could start small and do it manually for a few users, just to see if it gets traction. Later on, if you see that there is a market for such service, you can ask around to build a proper automated webapp with API integrations etc.