TRINEFLEX is an integrated EII-transformation toolkit following the `X as a service model ́. For the end-users (EIIs), TRINEFLEX will function as an end-to-end service managing the plant?s digital lifecycle and the process of transition to flexible and sustainable operation. This process will be enabled by advanced and green data acquisition, Big Data Infrastructures, process analysis, model development and finally Digital Twins with integrated multi-agent decision support systems. TRINEFLEX will be implemented at each of five demonstration sites with unique challenges, from 4 sectors: glass, copper, aluminium and water industries. The implementation will be supported through the integration of transformative technologies (from the energy efficiency, clean energy, sustainable fuels and feedstocks and CCUS sectors), that synergise with the powerful digital solutions to demonstrate flexibility measures towards energy neutrality. Additionally, TRINEFLEX is designed for rapid replicability in these sectors and high transferability in other P4Planet sectors centred on energy flexibility on the short term and industrial symbiosis on the long term. TRINEFLEX will mobilise local stakeholders and communities into new ways of interacting with the energy and process industries: Capacity building, open science, and introducing new forms of sustainable economic activity. Service- and community-based demand/response will be employed to leverage local energy resources, coupled with emphasis on sustainable fuels and feedstocks, accelerating the adoption of industrial-urban symbiosis.