ISEF MERT If the SMS doesn't arrive, then use another phone number from a different provider. Might sound stupid ("there has to be another solution!") but bunq cannot do anything about it and Paysafe doesn't care enough to change their SMS gateway provider.
SMS is a cluster** of a technology that nobody should ever rely on (but sadly some companies do) and issues like these are very frequent. Can't even really blame whatever provider Paysafe is using, I've been behind the scenes once. Imagine email, but instead of your IP packets just arriving at their destination (albeit sometimes slower than you'd wish) you have to make contracts with every single entity that provides SMS functionality to their customers.
As for an alternative to Paysafe: if you have any ideas, share them here. I'm not aware of another competitor that has that amount of market penetration throughout the whole EU/EEA. Of course, Viacash is objectively the better service, but unless they can expand to more countries that doesn't really help everyone.