Keeping Ubuntu from Going to Sleep

Here's how to stop Ubuntu from going to sleep.

Open a terminal

sudo nano /etc/systemd/logind.conf

Change the [HandleLidSwitch] line to [ignore].
It's prefixed with a #, so remove that.

If you'd rather not edit it in place,

#HandleLidSwitch=suspend
HandleLidSwitch=ignore

it's probably better to just add a new line right after the commented-out one, like this.

Once done, save with ctrl + O and exit with ctrl + X.

sudo systemctl restart systemd-logind

This reloads the config file and applies the change.

(I wonder if this is basically the Linux equivalent of re-sourcing your zprofile on Mac??)

And that's the setup done.

If you'd rather avoid the terminal, there's apparently an app called Tweaks.

sudo apt install gnome-tweaks

You should be able to install it with that.