Not an expert, but reading the article you linked it seems it was quite stressful?

> EPI demonstrated several results just after the Phase 2 end in 2026.[11] SiPearl demonstrated the Rhea1 chip running a complete HPC software stack. The system booted on a test board, with a standard Linux distribution running with high-speed HBM memories and their associated hardware performance monitoring counters. It successfully executed the HPL and STREAM benchmarks, demonstrating the readiness of the complete Rhea1 hardware and software ecosystem for HPC workloads to power Exascale systems. Rhea1 features 80 arm® Neoverse V1 cores, more than 61 billion transistors (7.8 billion equivalent gates), built-in High Bandwidth Memory, with 4 stacks of HBM, 4 DDR5 interfaces supporting 2 DIMMs Per Channel, and 104 lanes of PCIe Gen5 interface: up to 6 x 16 lanes + 2 x 4 lanes. Rhea1 was selected for implementation in Jupiter, Europe’s first exascale supercomputer. The next version, Rhea2, was selected for implementation in Alice Recoque, the second European exascale supercomputer.

And then more paragraphs how work was taken forward..