ThinkGeo Blazor is mapsuite 12.0 product. There are some breaking changes for the mapsuite 12.0. We re-organized the API. More detail is here https://wiki.thinkgeo.com/wiki/thinkgeo_12_change_log
We changed the name Proj2Projection. We call it ProjectionConverter now. So in the Blazor/mapsuite 12.0 you can do it like this
layer.FeatureSource.ProjectionConverter = new ProjectionConverter(4326, 3857);
All stuff under ThinkGeo.MapSuite.Shapes in mapsuite 10 now moved to the ThinkGeo.Core in mapsuite 12. And it support both .net core and .net freamwork.
Please let us know if you have any more question.