Bunq runs an independent, online banking platform - and, since its a dutch company, also a cost-sharing addon. Obviously. It is also important, that their main business is their app, not their website.
Bunq’s internet traffic, for a bank, is quite miniscule. Monthly bunq gets only around 16000 visitors in the Netherlands, 2000 in Germany - for other countries their website barely passes 1000 visitors.
Bunq started gaining traffic and recognition in late 2016, reaching their prime 20000 monthly visitors by the end of 2017. They never got back to these numbers after 2017 though, and keep losing traction.
Bunq gets most traffic through their app - from App Store and Google Play.
As for marketing bunq cooperates with big Dutch websites, which works for them very well - pin.nl, businessinsider.nl, usabilla, MasterCard, and nu.nl. They enjoy some attention via their blog posts on medium.com as well.
Bunq also invests heavily in paid social network traffic.