Hey Jens. Switch it back to 10, it will work fine. That config value is only to tell VizAlerts what style of URL to use when it links to a viz in an email. There was a change awhile ago that altered the way URLs were to be constructed, so it just helps it get them right. But nothing changed, URL-wise, between 10.5 and 2018.1, so a value of "10" is the appropriate one. I'll change or clarify this in the next version--thanks for pointing out this issue!
was a little bit unsure, but it is working as expected