This 2019 document, "GSGF Europe -Implementation guide for the Global Statistical Geospatial Framework in Europe" describes the harmonization of two standards:
INSPIRE D2.8.I.2_v3.1 of year 2014;
OGC's DGGS, "Topic 21: Discrete Global Grid Systems Abstract Specification", of year 2017.
Is there an official or experimental FOSS implementing these harmonized requirements?
NOTES on my personal interpretation. The 2019 document suggests that a solution is feasible. Checking Internet, seems that is possible to use FOSS solution (free and open-source software) for it. For example using DGGRID project... Or, for more a flexible Requirements 5, 7 and 8 of DGGS standard (the hierarchy of equal area tessellations), projects like S2-geometry and H3 Uber.