1. I noticed that I cannot associate a domain with a user or a group. Also I cannot add browse paths to say, platforms, or data process instances. Reason is there are some aspects (eg 'browsePaths' that are not compatible w/ certain *entityType*s). Is there anywhere a list of '_what-entity-is compatible-with-what-aspectName_'?

Please refer the Modeling -> Entities section from datahub docs. It contains docs for all entities as well as aspects available as part of that entity For example here is the doc for DataProcessInstance - https://datahubproject.io/docs/generated/metamodel/entities/dataprocessinstance

See it now - I had missed the Aspects paragraph header (is that even possible?) - THANK YOU