Last I heard about this, they did not fully commit on a singular technical solution yet. The closest I know being NGI Taler (FLOSS, created by a Swiss company, and plans a lauch in Euro this year), but it doesn't support offline payments yet, unlike what the digital euro's brochures say.
Hopefully this will be resolved, but I hear this is a very polarized subject since it would remove a lot of powers from the banks (by concentrating it around the ECB), and they are lobying heavily against it, and the right wing is listening.
The incredible CrossCode! Absolute gem of a game I wouldn't have discovered eight eyars back if they didn't have any Linux support.