A key challenge in quantum internet technology is connecting quantum processors at metropolitan scales. This study reports on heralded entanglement between two independently operated quantum network nodes separated by 10 kilometers, linked via 25 kilometers of optical fiber. The nodes host diamond spin qubits, and the entanglement is generated using quantum frequency conversion to the telecom L-band and an extensible phase-stabilized architecture. The system minimizes photon loss and enables real-time feedback for entanglement generation. The architecture supports full heralding of entanglement and allows for the delivery of predefined entangled states between nodes, regardless of heralding detection patterns. The system addresses key scaling challenges and is compatible with different qubit systems, establishing a generic platform for exploring metropolitan-scale quantum networks. The results demonstrate the successful generation of entangled states with high fidelity, showing the potential for future quantum networking applications. The study highlights the importance of phase and polarization control, as well as the use of single-photon detection and feedback mechanisms, in achieving reliable entanglement generation over long distances. The architecture is scalable and can be extended to connect multiple nodes to a midpoint, enabling the exploration of advanced quantum network protocols. The study also discusses future improvements, including enhanced signal-to-noise ratios and reduced decoherence, which could further improve the fidelity of entangled states. The work represents a significant milestone in the development of large-scale quantum networks.A key challenge in quantum internet technology is connecting quantum processors at metropolitan scales. This study reports on heralded entanglement between two independently operated quantum network nodes separated by 10 kilometers, linked via 25 kilometers of optical fiber. The nodes host diamond spin qubits, and the entanglement is generated using quantum frequency conversion to the telecom L-band and an extensible phase-stabilized architecture. The system minimizes photon loss and enables real-time feedback for entanglement generation. The architecture supports full heralding of entanglement and allows for the delivery of predefined entangled states between nodes, regardless of heralding detection patterns. The system addresses key scaling challenges and is compatible with different qubit systems, establishing a generic platform for exploring metropolitan-scale quantum networks. The results demonstrate the successful generation of entangled states with high fidelity, showing the potential for future quantum networking applications. The study highlights the importance of phase and polarization control, as well as the use of single-photon detection and feedback mechanisms, in achieving reliable entanglement generation over long distances. The architecture is scalable and can be extended to connect multiple nodes to a midpoint, enabling the exploration of advanced quantum network protocols. The study also discusses future improvements, including enhanced signal-to-noise ratios and reduced decoherence, which could further improve the fidelity of entangled states. The work represents a significant milestone in the development of large-scale quantum networks.