GTAO *is *in 4.24…
You need to enable it by r.AmbientOcclusion.Method 1. Some settings in the Post-Process Volume will affect GTAO as well, like Quality, Intensity, Static Friction, etc. But, GTAO is done at 50% resolution by default which can cause some ‘inverted halos.’ You can switch it back to full-res, at a cost obviously, with r.GTAO.Downsample 0. You can also toggle off the spatial or temporal filters with the same r.GTAO string, but disabling them will negatively impact the visual quality of GTAO(especially the spatial filter).