Europe has led the field of neutron science for several decades thanks to an active network of neutron sources. The landscape is currently experiencing dramatic changes as several facilities have reached the end of their life cycle. To help uphold Europe's position in the global research environment and further strengthen the network of facilities for research using neutrons, fifteen European countries are jointly building the world's most powerful neutron source in Sweden. The European Spallation Source ERIC (ESS) in Lund is now 43% complete. Its unique capabilities will greatly exceed those of today's leading neutron sources, enabling new opportunities for researchers in many fields, including material and life sciences, engineering, energy, the environment, cultural heritage and fundamental physics. Following the prioritisation of ESS by ESFRI and the Competitiveness Council, eighteen partner organisations successfully delivered the Horizon 2020 project BrightnESS, from 2015 to 2018. BrightnESS-2 will build on the legacy of BrightnESS, but shifts the focus from risk mitigation to long-term sustainability of ESS and its community. This both supports, and depends upon, the long-term sustainability of a vibrant neutron scattering community and a network of complementary facilities in Europe. With a timeline of 42 months, and 16 partners from Europe and South Africa, BrightnESS-2 will ensure that i) neutron facilities in Europe provide access and services in a strategic and coordinated manner to user communities from Europe and beyond, ii) in-kind contributions to ESS are managed as part of the R&D collaborative work, iii) ESS boosts the innovation potential of the facility and fosters strategic partnerships with industry, iv) ESS reinforces its position as a truly global research infrastructure, v) ESS delivers positive socio-economic impact. The proposal has been endorsed through Letters of Support by 13 institutes and neutron sources from around the world.