This is a link-post for an explainer of NASA's Double Asteroid Redirection Test (DART). It may be one of the most prominent existential risk reduction activities in the public sphere (the explainer even describes the likelihood of asteroid collisions large enough to threaten civilisation). I hadn't seen much talk about it.
DART will be reaching a two asteroid system in the evening of September 26. It has been travelling for around 10 months, and is now around 11 million kilometres away. The asteroids are not a threat to Earth in any way. It will autonomously target the smaller asteroid (Dimorphos, around 160m diameter) and collide with it at a speed of around 26,000 km/hr.
This should inform the potential for future asteroid-redirection efforts. As noted in 'The Precipice' though, while potentially reducing the risk from asteroids, such a capability may pose a larger risk itself if used by malicious actors to target asteroids towards Earth.