I have been trying to get another system drive working and somehow I have screwed up my main drive.
It no longer will boot into KDE, I get a console login prompt instead followed by when logged in
systemd-readahead[376] failed to open pack file - system readonly (or something close to that)
Just a guess but if the partition file system is corrupted it may only load read only. Boot to a live Linux and run fsck against the various Linux partition on the drive.
Press esc immediately after the boot selection in grub to get a text based init screen it may show what is broken.
If you accentually overwrote one of the Linux partitions in your attempt to fix some other system drive, you may just have to reinstall :’(