I've found a partial answer after many hours of study and trial and error. First, I divided the project into a
Razor Class Library (RCL)
using the shared pages, models, classes, tag helpers, extensions, styles, and so on. the even
, therein:). Additionally, my "domain-specific overrides" are in the other project. It works quite well.
I used this to generate my RCL: develop reusable UI (of course...)
I used this to register the interfaces and the DbContext: How to introduce services
And I used this to embed "static" files (js/css): Static Resources Included
The last steps are to upload the various domain-projects to the domains and register the dlls of my shared RCL on the webserver. Although I haven't tried it yet, it appears rather simple.
Although this solution meets my needs, it may not be the ideal one. Feel free to share further solutions!