Honestly, on mobile, there isn't really anything. However, if you're burdened with an iPhone (like me), I'd say use iMovie.
If you're on Android and you're clever, you might be able to use FFmpeg from inside Termux.
If you have a particularly powerful phone, you might be able to install a window manager (most people go for Fluxbox) and a lightweight video editor (like Avidemux) in Termux, share your screen with a TigerVNC daemon, and then use a VNC client on Android to access it. It will most likely be slow and a little choppy, but it might just work if you seriously have no alternative.