As the 2030 deadline for the Sustainable Development Goals (SDGs) approaches, higher education institutions (HEIs) are under increasing pressure to contribute meaningfully to global sustainability efforts. In response, a growing number of digital innovation networks have emerged--transnational, platform-mediated collaborations that connect universities and partners to advance the SDGs. Despite their expanding role, the governance dynamics of such networks remain under-examined. This study investigates how five prominent digital SDG networks in higher education--HESI, SDSN, UGC, COPERNICUS Alliance and AASHE--are governed and how they coordinate action, foster trust and navigate digital mediation. Using a document-based digital ethnography approach and a "simulated participant" perspective, we analyse publicly available data from websites, reports, event recordings and online platforms to reconstruct network practices. Guided by network governance theory, the findings reveal three recurring dynamics: adaptive coordination beyond hierarchy, the construction of "digital trust infrastructures" and the balancing of global missions with local contexts. These networks, while fragile, demonstrate how distributed leadership and digital tools can sustain collective engagement. The study contributes to theoretical debates by extending network governance theory into the digital and transnational domain of higher education and identifies design principles for building robust, inclusive and responsive academic networks. A future research agenda is proposed to address questions of legitimacy, equity, platform governance and long-term impact. As universities reimagine their role in sustainability, understanding how digital innovation networks function is essential to transforming higher education into a globally connected force for sustainable development.