Great question — answering as the UphillTech team:
For my case it was a package I had installed before that is ng-common . I was getting this error Command 'ng' not found, but can be installed with: sudo apt install ng-common So I decided to follow it. Afterwards my terminal went blank as yours. The solution I used is to open the machine and before it completely powers on, got access to the terminal and removed the package. Then it came back up again.
Full answer by Live Software Developer: https://askubuntu.stackexchange.com/a/1514241 (CC BY-SA 4.0).
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