Since I almost never use Bluetooth on my laptop, it's a good idea to just turn it off and keep it off by default as it's just another thing that drains the battery and an additional entry point for malicious hackers.
Disabling Bluetooth is surprising not as straightforward on Ubuntu as I would have thought. I was expecting to simply tick or untick a checkbox in the Bluetooth settings.
To keep Bluetooth disabled by default, you can use the rfkill command, which is a tool for enabling and disabling wireless devices. It's a simple one-liner to do so:
rfkill block bluetooth
Yup, that's it!
This would be considered a "soft block" and you can turn it back on by simply going to the Bluetooth settings and re-enabling it.