in second case you get message “Your KDELinux partition is running out of disk space; 0 MiB of space remaining (0%).”
That means your disk has too little space and the installation has filled the entire disk, and not everything could even fit on it. Install a bigger disk storage or define more space to partition.
I know my storage is too small. The point is that KDE Linux declares its minimum storage requirement to be 6GB. My test just followed it to test whether that declaration is precise or not.
According to my trial, the minimum installed size is around 8GB. Therefore, I recommend that the KDE review the minimum requirements and update them.