Android system update stuck for every My phone is Pixel I. I got a notification for the latest Android 8.0.0. The screen says it is updating, and it has been two weeks...looks like it is not going to finish forever.

There's no indication whether it is ongoing, or is stuck. No button to stop/restart.

Any idea how to fix this?
It possibly has encountered an error updating. Stoping it will render your device unusable which I'm sure is your only option right now. If you had unlocked your bootloader you can do this: https://www.androidcentral.com/how-manually-upgrade-pixel-nexus