The selection of digital collaboration platforms impacts research participation in international digital humanities projects. This study emerged from practical challenges during the “Ted Stamm: Tags” project, a multi-institutional art historical research initiative transcribing 63 sketchbooks (1973–81) with 675 documented participant contributions. Initial reliance on Google Sheets was discontinued due to ethical concerns regarding policy changes, while the subsequent transition to Microsoft Excel created barriers for external collaborators across different institutional frameworks. This paper investigates alternative collaborative platforms that meet European standards for data sovereignty while supporting multi-institutional research collaboration. The research question asks: What European alternative platforms exist that provide institutional compatibility and GDPR compliance without sacrificing collaborative functionality? Through a case study methodology grounded in Tags transcription project, this paper proposes an evaluation structure and planned comparative assessment of three European platforms: kSuite, LibreOffice, and Proton Drive.