Years ago I was into keeping tropical fruit trees/bushes indoors. One of them didn't do well under my care so I planted it outside to enjoy the final year before European winter gets it. It somehow survived, barely. Each year it did better though so 5-6 years later it's full of edible fruit. I don't know what it is. Can somebody identify it?
It appears to be a cultivar of Jujube (Ziziphus zizyphus) also known as Chinese date - https://en.wikipedia.org/wiki/Jujube
This is based on JimN's correct observation. I looked at a few dozen images of Ziziphus Zizyphus - both fruit and leaves. They appear to be identical. The fruit tastes as described. The fruiting progression matches the description in Wikipedia.