Does anyone know anything about, BlackFin Capital Partners?

FS focused PE firm, like most in the space decided to switch away from pure-play asset heavy financial services and pivot into software-driven businesses like payments, FS infrastructure (core banking systems for instance), productivity software selling into FS, wealth management, insurance brokers etc. The space is quite fun and the assets interesting (bar the sky-high valuations you meet here and there) and if I remember right they cover most of Western Europe. 

Not sure about what you found on the internet, but their website is pretty comprehensive (raised a 900+m fund in 2019 after another one less than half the size in 2016). Interview-wise you shouldn't expect typical FIG questions but more software/ SaaS focused - definitely familiarize yourself with SaaS specific metrics ranging from ARR, churn, net and gross retention, maybe even cohort-level analysis if you've never touched it before. Also makes sense to build a view around at least one large FS vertical in Europe (for instance clunky banks, some still reeling from the GFC or the sovereign debt crisis in Greece, with bottom lines killed by the low interest rate environment and ran on legacy systems, desperate for any cost reduction conceivable under the sun).