Just received the product and will answer my question myself. Ea works with HomeKit and is the newer eve product that also supports the new Matter standard. Why it is cheaper. nobody knows...

This version requires a HomeKit Hub with Matter standard support. This means that other hubs will no longer support this "Matter-only" Eve Plug. The following HomeKit Hubs support Matter (https://www.evehome.com/en...):

- Apple TV 4K (3rd gen, 128 GB).
- Apple TV 4K (2nd gen)
- HomePod (2nd gen)
- HomePod mini

The older "HomeKit-only" Eve Plug (currently the more expensive plug) can be updated to Matter. There is no way back from Matter to "HomeKit-only". So if there is already a "Matter" hub in the house, you can take the cheaper one, otherwise you must take the older one, which can then be updated to Matter later if desired.

I.e. the more expensive version supports both options, the newer, cheaper Eve Plug necessarily needs Matter. In practice, all devices are then visible in Apple HomeKit, whether "Matter" or not. :-)