This volume is not formatted as APFS

There is nothing strange about it. Catalina and Big Sur require that a disk be formatted forAPFS. If you wish to upgrade, first back up your hard drive. Then you will need to use Disk Utility to reformat the HD, then download and install Catalina. Finally restore your files from the backup.

JoeTesla wrote:

When I try to install the upgrade to Catalina, I get the message above for my boot drive. I am currently running 10.14.6 (Mojave) and the drive is formatted as Mac OS Extended (Journaled). This is REALLY strange! And after reading some of the message today, maybe I'm better off not getting the upgrade to work. Any thought on what to do about this? Thanks!!

Not an issue— Non-Destructive APFS Conversion, It is a surprising fast and efficient conversion.

How to Upgrade to APFS if Not Done in macOS High Sierra Installer - The Mac Observer

https://www.macobserver.com/tips/how-to/upgrade-mac-apfs-after-high-sierra/

Restart the Mac into Recovery Mode.

Recovery: https://support.apple.com/en-us/HT204904

Launch Disk utility:

Click-select your named boot volume—the default name is "Macintosh HD" —(Not the physical drive above it.)

In the Disk Utility> Edit menu> select “Convert to APFS"

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or

If you download the Catalina installer, Quit the installer like any other app if it launches./

Here it will sit harmlessly in your Applications folder. You can make a bootable USB installer:

How to create a bootable installer for macOS - Apple Support

https://support.apple.com/en-us/HT201372


Boot to this installer holding the option key and from the "Startup Disk Manager" select it for boot.

ref: How to select a different startup disk - Apple Support https://support.apple.com/en-us/HT202796

The installer contains a DisK Utility.app among other Utilities/Tools—

Now that you are not mounted to your internal SSD— you can Convert to APFS on the fly (non-destructive.)

Disk Utility>Edit>Convert to APFS

*please note from DU>View>Show All Devices for clarification—

You are selecting your "named boot volume" (not the physical drive above it.)

Always advised to have a current redundant backup plan before any update/upgrade/conversion—only in this way can you restore your User if something goes UN-expectantly sideways.

All I can say is that when I upgraded from Mojave to Catalina the installer took care of everything. I did not have to erase and reformat my hard drive. I have seen absolutely NO documentation from Apple stating that the user must erase and reformat their hard drive before they can move from Mojave to Catalina. Can you imagine the cacophony that would have caused for millions of users.

Using Disk Utility the user can convert volumes to APFS without losing any data so I assume the Catalina installer can also. When I installed Mojave I was given the option of converting to APFS which I did.

Agree with @ Ronasara - will have to convert the HFS to APFS. As mentioed - will loose everything on the drive during the conversion. So follow the advise of @ Ronasara