Hey jabberwokz. I'm sorry to hear that your game keeps closing for some reason. To start out, please uninstall your current Ubisoft Connect launcher and reinstall with a fresh download here[ubisoftconnect.com]. This issue can sometimes be caused by an out-of-date launcher. Secondly, I recommend verifying your game files to ensure no installation or patch files have been corrupted, and try any steps from our general troubleshooting guide[support.ubisoft.com] that you haven't yet.

Should this issue continue, I encourage you to reach out to our team on the Support Portal[support.ubisoft.com] and create a case with your system files[www.ubisoft.com] attached. They would be happy to look into this more with you!