This solution is easy to use, 100% local, and works very well with static watermarks.
Required Node Packages
ProPainter Nodes (must have)
Video Helper Suite (or any load/save video nodes)
KJ Nodes (or any other image resize node)
Usage
You need:
a video containing a watermark ;
a mask: a totally black image, with a white rectangle on it delimiting the zone of the watermark to remove.
🟢 Load your mask in the node Load Mask IMG and your video in the node Load Video. Click Run. End.