Ubuntu 20.4 crashes / freezes whenever there is yet another update

I’m running Ubuntu 20.4, and I had set my update-options to “weekly” (security updates “display immediately”), the live patch option was switched off.
Whenever there is an update (security, Ubuntu, just Google browser…), the whole system freezes and is unresponsive. This is especially annoying if you’re waiting for a calculation that already took all day, return to your machine in the morning and see … it’s crashed… once again

It’s great that people are working so hard to improve the system and everything… But could you PLEASE add an option to TURN OFF updates completely (yes, the security updates as well)?

And my questions:

  • Is there a way to disable the updates completely (I set it to “never” now, but there is no way to get rid of the security options, disconnecting my machine from the internet is no option as it uses access to databases for the calculations I need to do)

  • Is there a way to get the crash log after the restart?