To write down only the essentials for the answer:
The magic spell sudo akmods --rebuild --force “re-installs the Nvidia drivers if they badly updated”.
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It’s suppositely manageable to “understand what to do” by using this:
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In the end I have no true idea why this happens (seems like Nvidia drivers “need time to properly completely install, but they don’t show a UI-progress_bar [updating via Konsole instead suppositely tells you when it’s just done & done] so you just have to wing it”) so I’d not be surprised if this happens again.
At least, for what Official Nvidia Drivers are concerned, it’ll not be many more times…