We should probably measure how many login / signup actions are started but not finished with SUL3.
It's possible to have an interrupted login with SUL2 (or MediaWiki core) when there are multiple steps; e.g. you submit username/password, you get a 2FA check, and you just abandon the page at that point. But it's rare, since multistep login is itself rare. But with SUL3 login will always be multi-step (even when it doesn't seem so from the user's point of view) because the redirect to the central domain counts as a step; so if something goes wrong and the user does not find their way back, it will be much easier to end up with an interrupted login, which wouldn't show up on our current dashboard that only counts successes and failures.
So we should track the number of logins started, and chart started - (succeeded + failed).