I never got a proper response from Ubisoft - only a message saying that they're busy because of corona.

My solution was to get a refund from steam and buy it from uplay. That was the only way I could get it working.

Unfortunately I had to go through a bit ofd a struggle with steam customer service because first they denied the refund based on the play time during free trial. A lousy excuse but eventually they agreed to the refund.