NLnet foundation is a foundation that may be of interest for people working on software supporting OpenStreetMap.
It self describes as "financially supporting organizations and people that contribute to an open information society. It funds those with ideas to fix the internet"
StreetComplete is one of projects that received support as part of Next Generation Search and Discovery. Justification was that OpenStreetMap is a fundamental provider of geodata for any private search engine, and improving StreetComplete is improving OSM ecosystem in general.
There is open call for proposals ( https://nlnet.nl/useroperated/ ) that intends to fund projects helping to create "healthy, resilient, sustainable and fair internet" / "open, trustworthy and reliable internet for all". This likely can be also considered as covering projects helping OpenStreetMap.
- this was written by person who received such funding