Sustainable entrepreneurship and digital legitimacy in European Union

The construction of the European Union's "digital single market" faces a paradox: improved availability of digital public services and infrastructure coexists with lagging uptake of mandatory digital administrative and compliance procedures by small and medium-sized enterprises (SMEs). Based on the European Interoperability Framework (EIF), this article reconstructs interoperability across different national legal jurisdictions and administrative systems as a market access condition and advocates for the proposal of "Institutional Middleware" as an interpretive mechanism to reveal how digital legality generates operational barriers and process inefficiencies at the legal/organisational level. Methodologically, this article adopts multi-source evidence design: firstly, we build the "Adoption Gap" index to quantify the gap between government service availability and enterprise usage rates; secondly, we combine e-government obstacle data and enterprise digital intensity index to identify the disproportionate compliance burdens on SMEs; finally, we verify the implementation efficiency of institutional tools through the hierarchical mapping of funds, standards and procurement rules and urban cases. The study found that the fixed cost of adapting internal workflows to external regulatory standards constitutes a hidden barrier for SMEs. The contribution of this article is to advance the perspective of institutional Middleware and to demonstrate how the EU can encapsulate compliance complexity into a reusable public infrastructure through policy combination, thereby providing large-scale institutional conditions for a sustainable entrepreneurial ecology.