Did this once on a router in a datacenter that was a flight away. Have remembered to set the reboot in future command since. As I typed the fatal command I remember part of my brain screaming not to hit enter as my finger approached the keyboard. 🤦‍♂️

Is mysql in your repolist? The second tutorial adds it; just wanted to check that it worked.

The Mint team removed snap intentionally and explain their reasons here: https://blog.linuxmint.com/?p=3906