Interesting issue then. We got a Becker transponder installed and certified by the local authority (LBA) in 2006 which includes a connection to the GPS and position report available via the extended squitter. Might be that that was a grandfathered installation, but it is still flying today and allows ADS-B out.
Interesting that EASA made that into a major issue now, but the reason might be the issues around position data integrity which most if not all GA installation do not provide which means that ADS-B reports have to be discarded by ADS-B in systems anyway.
Interesting though that ADS-B out will be mandatory in less than three years for certain aircraft (more than 5,7t or 250kts cruise speed) within europe but the certification standards are not yet published.