There are some organisations/groups which seem to be effective in actually paying people.

There is a group of Debian developers that collect funding and pay Debian developers/maintainers to maintain LTS for Debian releases:

https://www.freexian.com/en/services/debian-lts.html

https://raphaelhertzog.com/tag/Freexian+LTS/

The FreeBSD Foundation also hires developers to do actual work:

https://www.freebsd.org/news/status/report-2016-04-2016-06.h...

https://www.freebsdfoundation.org/what-we-do/projects/#curre...

However, I think such initiatives are typically highly underfunded. Like OpenSSH/{Open,Libre}SSL/GnuPG, everyone uses the software, few companies/individuals chip in in a significant way.