I asked Linktap if they had any experience of the Gardena system and got this reply.
To use Gardena smart water timer, user also needs to buy a Gardena Gateway and two water timers. They are much more expensive than LinkTap’s.
According to our German customers’ feedback, Gardena’s smart water timer is not that smart. It does not have as many features as ours.
Our G1S/G2S have just arrived in EU. They are available in amazon.fr now.
I can also say from personal experience that LinkTap support is excellent and their product is really good quality.