RivEX is an ArcGIS Pro 3.7 Toolbox, it is not compatible with 3.5 or earlier versions of ArcPro
It does not require any expensive ESRI extensions
Runs under the Basic (Creator User Type) ArcPro license level
RivEX is designed to access data in a File GeoDatabase and not from Enterprise/Portals
Requires you to have installed a specific version of the shapely module (more advice here)