Michael Ford, who contributes as fanquake, is a Bitcoin Core maintainer. Brink funds him full time, and describes the scope as his maintainer work plus the build system, security, and reducing the number of dependencies the codebase carries.
Dependency reduction is the least glamorous item on that list and arguably the most load-bearing. Every external library a consensus-critical program links against is code that nobody on the project reviewed, shipped to every node operator, and capable of splitting the chain if it behaves differently on two platforms. Cutting them out is slow work with no feature to announce at the end.
He is one of three people whose PGP keys are published in the Bitcoin Core repository for reporting security vulnerabilities, alongside Ava Chow and Niklas Gögge. On the funding arrangement he has said that full-time, long-term sponsorship is what lets him spend all of his time contributing to and maintaining Bitcoin Core.