Open source always surprises me, GIMM-VFI exceeds the video frame interpolation I've used before, and now kiji has quickly implemented comfyui nodes for it.

https://github.com/kijai/ComfyUI-GIMM-VFI

Using it, a video with a very low frame rate can be made very smooth.

Go ahead and try it out.

If you don't have a suitable local environment, you can try it at https://www.comfyonline.app/explore/21895650-8795-4bb9-be30-939637b67d17