NEO TRON imo
NEO is popular in Asia. We do not have kiosks in that region
Only btc I think would be the best option considering the market cap and people who own it is the highest compared to any other coin. So if you place some small coin in ATM hardly few people may use it and to run the ATM we require highest number of footfalls and only btc coin can provide that at the moment.
BTC is slower and more expensive. Sometimes it's more efficient to buy some crypto by getting Ripple from Trovemat, and then making XRP-->BTC-->and so on..
Plus some regions have specific preferred crypto, like Japan 🇯🇵 and China 🇨🇳
