Mastodon, an alternative social network to Twitter, has a serious problem with child sexual abuse material according to researchers from Stanford University. In just two days, researchers found over 100 instances of known CSAM across over 325,000 posts on Mastodon. The researchers found hundreds of posts containing CSAM related hashtags and links pointing to CSAM trading and grooming of minors. One Mastodon server was even taken down for a period of time due to CSAM being posted. The researchers suggest that decentralized networks like Mastodon need to implement more robust moderation tools and reporting mechanisms to address the prevalence of CSAM.
Tor (The Onion Router) was invented by a United States Naval Intelligence Unit. They released the source code as open source and handed control over to the EFF but several US Government agencies continued to provide substantial funding (especially the Bureau of Democracy, Human Rights and Labor Affairs). As far as I know they continue to fund it.
There are definitely examples of Governments funding open source software, especially things that are as valuable as a social network.