After an long search, I finally found an amazing video crop app.
https://crop.mov

Features:
========
✔️ Free & Open Source
✔️ No software install
✔️ Cross platform / OS support
✔️ Works on any device [even Raspberry Pi]
✔️ Works in any browser
✔️ Simple UI with video preview
✔️ No watermarks
✔️ Privacy: your videos stay on your computer
✔️ Crop [free or preset], Trim, Flip [V/H], Mute Audio
✔️ Displays WxH Pixels during crop
✔️ Displays Frames during Trim
✔️ Uses FFmpeg Web Assembly

Credit: https://github.com/mat-sz/crop