Ubuntu? I am running Debian servers for over 10 years with apt-upgrade and dist-upgrade; never had any issues. Ubuntu ones had several issues but all fixable with a bit of handywork in rescue mode (if available; if not you are often screwed).
This is just a quirk on vultr. Not to do with ubuntu or debian. If you create an ubuntu server on vultr, it does an apt-get update immediately. So, if you 'jump' and immediately run apt commands, they fail.
This is because it runs apt daily on startup. Been bitten by this many times on vultr.