RE: Appstore applications end up with login-dialog tonight
I dont have much to contribute with, except that we have had the exact same experience a couple of weeks ago.
And it is like Jens i saying, once the tenant have moved to SuperID, you just need to login with the new experience and everything is back to normal.
Regarding the samesite issue,
In our experience, the result of that is not beeing brought back to the loginscreen, but an endless loop.
Or, if you are using the latest version of Service onSite, you will recive an error 302
This error is solved by adding this for Apps
<sessionState timeout="120" cookieSameSite="None" />
<httpCookies httpOnlyCookies="true" requireSSL="true" sameSite="None" />
</system.web>
And to solve samesite error 403 onSite, update Windows and restart the server.
Just my two cents