OpenAtlas

Update
It is now possible to also add polygons (instead only rectangles).
New package needed:

sudo apt install python3-svgwrite

Original description
In the first version, a rectangle geometry will be available for annotating. It is planned to include more geometries, especially a polygon.
The complexity is not the Leaflet annotation, but the creation of a valid IIIF manifest and the SVG selector for the IIIF Presentation API 2.