After installing ArcGIS Pro 3.0 and Discover, I am unable to open any Discover geoprocessing tool and receive python errors.
Solution
Please browse to the folder below -
C:\Program Files\dotnet\host\fxr\
And delete the subfolders except for the highest version one, which is probably "6.0.13".
If the issue persists, reinstall the .NET 6 framework. More details are in this ESRI KB -
https://support.esri.com/en/technical-article/000027925