Live KDE install doesn't show tag for installing

The errors you see booting up in the live image are generally fine and can be ignored. With that said, I cannot reproduce your issue with the latest KDE live image.

Booting it up, I see this.

I will assume this is your reddit post. Installing the system and setting up a user, everything works as intended.

I would suggest redownloading the live image. Or specifically download the image that has the date like here.