We have had to update our code signing certificate this year in a way that caused some compatibility issues because the private key size I used in 2009 is no longer acceptable. I am not positive that this is the cause of your issues, but it might be.
I tried running Skyline-daily on all my computers and some of them had this unexpected behavior where this standard system upgrade message is shown instead of the custom one I implemented years ago. However, when I went ahead with the installation, I always ended up with a working Skyline-daily 23.0.9.187 installation that did not show any further messages when it was started.
If this is not the case for you, then you should consult this page on how to deal with a broken installation:
https://skyline.ms/install_recover.url
Sorry for the inconvenience. Hopefully, this is a minor speed bump and we will not need to make an update like this again in a decade or more.
--Brendan