This work related to improved and extended real-time and co-simulation as well as Hardware-in-the-loop experiments covers a broad range of different but related topics, with a common focus on the interconnection and integration of Research Infrastructure in the form of simulators as well as physical laboratory equipment applied to: Multi-domain co-simulation, Mixed continuous and event-based co-simulation, Local and remote Hardware-in-the-loop testing, Virtual interconnections of multiple physical laboratories, and Virtual interconnections of multiple real-time simulators. Due to the broad range of topics covered in the work plan and the large number of partners involved, it was necessary to start with a more precise definition of the work scope. For this purpose, a survey was made among partners, asking for interests and experiences in seven different topic areas to identify clusters with enough interest. The results were then compiled into a scoping proposal. An online workshop was held with all involved participants in order to formulate concrete research topics, and subsequently to define goals and intermediate steps for each of these topics. The work related to multi-domain co-simulation aims at furthering the state-of-the-art in this field to enhance usability, flexibility, performance, standards compliance, and reproducibility of related approaches. Moreover, the work on real-time coupling and Hardware-in-the-loop-based testing aims at improving, analysing, and evolving methods and algorithms for coupling real-time systems – physical or simulated – with a particular focus on systems whose components are geographically distributed. This report summarises related methods and tools developed in ERIGrid 2.0 focusing on concept development rather than implementation and proof-of-concept. The latter will be the subject of other, project-related reports.