In the “see also” section of that page, there is a very exacting assessment of Gramps’ quality and shortfalls with standard 5.5.1 GEDCOM imports:
- Cardinal, John. “GEDCOM Assessment v1.05” evaluating GEDCOM v5.5.1 import using Gramps AIO64-5.1.2-1 with the " assess.ged v1.05" test file, 7 Mar 2020 (GEDCOM Assessment change log)
There’s also a thread about other 3rd party reviews of the Gramps GEDCOM implementation: