It's complicated, there are two types of applications and networks.

1) Direct payment systems via mobile phone, generally designed initially for payments between friends and family. They have been set up in several countries by neobanks, generally based on the Mastercard network (very common among neobanks). A Latvian neobank may expand into the Baltic countries, but is unlikely to succeed in Portugal. These systems are not interoperable with each other.

2) Systems promoted by banking networks, such as Bizum in Spain, which has expanded to the Iberian Peninsula, and Wero, which is supported by BNP Paribas (France, Belgium, Germany). These networks are independent of Mastercard, Visa, etc., but they seek to favor their members and do not seek to become widespread.

Discussions have been ongoing for years to achieve interoperability. The idea for the moment was to let the market structure itself naturally without too much intervention, other than to say “we must move towards interoperability at the European level.” This approach has worked very well for bank transfers, which have become simple, fast, and relatively secure, but it has taken a long time (Europe, consensus, etc.).

Here in Belgium I have the impression there's steady progress towards such a system: https://wero-wallet.eu