The NLnet Foundation supports organizations and people that contribute to an open information society. It was influential in spreading the Internet throughout Europe in the 1980s. In 1997, the foundation sold off its commercial networking operations to UUNET (now part of Verizon), resulting in an endowment with which it makes grants.<p><a href="https://en.wikipedia.org/wiki/NLnet" rel="nofollow noreferrer">https://en.wikipedia.org/wiki/NLnet</a>
The Sovereign Tech Fund: <a href="https://sovereigntechfund.de/en/" rel="nofollow noreferrer">https://sovereigntechfund.de/en/</a>
There are a bunch of grants listed on the FOSSjobs wiki, please add any more you find:<p><a href="https://github.com/fossjobs/fossjobs/wiki/resources#grants">https://github.com/fossjobs/fossjobs/wiki/resources#grants</a>
The EU framework research programs have strongly favoured FOSS contributions. It's certainly not the most straightforward application process though and competition for the grants outside niche domains is cutthroat.
FOSS Funders is a community of companies that sponsor FOSS maintainers and projects: <a href="https://fossfunders.com" rel="nofollow noreferrer">https://fossfunders.com</a>
A lot of these providers of grants to open source don't actually use open source themselves, so you can't apply without enabling proprietary JavaScript, joining their Slack etc :(