OBS does allow you to record at low frame rates ! It goes as low as 10 FPS in the presets, but I think you can input lower manually.
I use that for video, but for stuff where I want snapshots or really short ultra low FPS video I use lovely free ScreentoGif, which has 2 modes - one for video and another for manual snapshotting, which just draws a frame over C4D, and you manually hit the snap button whenever you like. It has comprehensive editing, annotation, and retiming as well, which is nice. Here's one I did in that earlier...
CBR