I've been trying a few things to get wifi working on a fresh Zorin installation (link), and I now realize I'd like a way to completely undo previous system changes and revert to a completely fresh Zorin before trying new steps.
How can I do this? Is there an in-built terminal command? Or do i need to install timeshift or something else?
As far I know, re-install would be the only choice. Timeshift would've been helpful for exactly this type of situations, but only if you already had some snapshots to restore from. Installing it at this point and taking a snapshot would only help to revert to the current state. For a complete fresh start, a new installation is needed.
Thanks, I'll do a fresh re-install and set up Timeshift before I attempt any more changes to get wifi working.
Fortunately with the SSD in the new machine, the install process is pretty quick.
Doh! I spoke too soon. Upon trying to reinstall, the installer offers to:
I see no direct option just to replace the existing Zorin.
I guess I have to choose "Something else" but I'm not sure what to do then.
There is one partition "/dev/nvme0n1p5 (ext4)" labelled as "Zorin OS 16.3 (16)". But I don't know what to do. Just click on it and then "Install Now"?
Yep, that is the right choice.
This will open the partition manager. Click on the ext4 partition (you can show a screenshot or screen photo if you need confirmation) that has Zorin on it.
Click the (-) icon on the toolbar.
That will delete the partition and list it as Free Space.
Now, click on the Free Space you just made and click the (+) icon on the toolbar. This will open a popover window to format that partition. Format it as ext4, primary, set the size if you want / need to do so. Set as at beginning. Be Sure to set the Mount point to /
Once formatted, proceed to install.
Do you mean I should select the radio button for that partition in the "Format?" column?
No.
When you select the free space, then click the (+) icon, then the popover to format that partition will appear.
Yes, I did click + etc. The radio button is visible (but unselected) after doing that.
Following the above steps, the partition first becomes free space, then (after clicking + etc) gets marked again as "Zorin OS 16.3 (16)"; selecting it, not clicking the "Format?" radio button and clicking "Install Now" results in the following message:
Do you want to return to the partitioner?
The file system on /dev/nvme0n1p5 has not been marked for formatting. Directories containing system files (/etc, /lib, /usr, /var, ...) that already exist under any defined mountpoint will be deleted during the install.
Please ensure that you have backed up any critical data before installing.
Go Back - Continue
Do I continue, or go back? 
I may not be picturing what you are describing correctly.
You are to format the partition - then proceed to install Zorin OS after formatting.
If you are seeing a radio button within that Popover window that sets the drive as primary, beginning of space, mount point as / and so on - then yes, select it.
I have never seen a radio button there before... 
You have that selected and you can see the (-) is clickable on the lower left (Next to the button marked "change"). You can see that the (+) is grayed out.
Click the (-) button.
Next, click on the same line that was the ext4 partition and now is Free Space. The (+) should now be clickable and not grayed out. Click the (+) button.
This will open the above mentioned popover window.
That's what I did, and this is the result.
After turning it into free space and then doing the pop-up /ext4 / primary etc, it returns to saying "Zorin OS 16.3 (16)" the same as before the whole process. 
Are you able to show an image of that popup?
Ok, going through the process again (select partition, click -, then click on free space, click +, get popup, set to "Primary", "ext4" and "/".
Everything there looks good. Once you click "OK" It should format that partition.
Once I click OK, I get that partitioner window with the radio button deselected and if I click install now, the message asking if I want to return to the partitioner.
You are booted in the Live USB Media, correct?
Is that drive unmounted or mounted?
I don't know if it's mounted, but it's listed (twice) in the Install partitioner.
In between is the laptop's SSD, /dev/nvme0n1 (with the various partitions for Windows, Zorin, EFI etc).
The column "Mount point" is empty for all drives and partitions.
This would be the LiveUSB Zorin OS "Try Zorin" Installer.
This would be your baremetal installed Zorin OS.
I am actually stumped. I have never seen anything like that happen, before.
Maybe 4box should fire up Gparted from Live USB and post a screenshot before trying an install.
The "Something Else" method caught me out on Z16 as is different from Z15 and what I was expecting. But I do not recall seing that Format column.
