It's been about 3 months since the kde upgrade, which required some manual intervention to get it done. There were plenty of posts at the time discussing how to do it as it wasn't straightforward but could be done with a little patience. It appears you've missed all that. I suspect time has flown by and your impression you've been upgrading monthly has slipped a little. The recommended frequency of upgrading is weekly or monthly at the outside. If your upgrade history is set to delete after a week (the default setting), it's not possible to settle when you last ran it. If you've altered that setting (as I always do) you will have a record. The KDE upgrade needed changes to sources.list, and since then there's been some trouble with the repo which needed a move, and a further upgrade of sources.list, so I suppose it could just be possible if your timing was unfortunate that your last upgrade or two might not have been complete.
Anyway, the point is, as O-P says, you now need to install task-kde-minimal to begin rebuilding your system. That should get you back to the desktop, though it won't re-install much more than that, so you might have to put some applications back, but at least you'll have a desktop to work from.
