If you want something really barebones, install this OBS plugin: https://github.com/scaledteam/obs-image-reaction/releases/ (that's what I used before I made my custom SVGtuber setup)
If you want something that's well-established and widely used, I know a lot of people like https://veado.tube/ (although I personally am not a fan of the way it does chromakey)
If you want something more feature-rich, @rahisaurus made this really nifty tool: https://rahisaurus.itch.io/rahituber
