Can't add an APFS volume as a Time Machine backup?

It is still recommended by Apple to keep your Time Machine backups on a Mac OS Extended (Journaled)

formatted drive.

Open Disk Utility click on View in the menubar and select Show All Devices.

Now highlight the Disk not any of the indented Volumes and click Erase

Give the Disk A name,

Format: Mac OS Extended (Journaled)

Scheme: GUID Partition Map

Click Erase.

When Done you can then re partition your drive and set it up as you wish.

Snufflepuff wrote:

1. I bought a new external drive to use for storage and backup. I was planning to partition it, as I'd done with previous disks, into two pieces. Then I learned from Disk Utility that nifty APFS formatting is more flexible than old-fashioned partitioning, so I chose to create 1 volume for laptop backup and 1 volume for extra storage.

Now, I'm unable to add the newly created volume in the Time Machine Preferences.

Did I do something wrong and/or is APFS the wrong choice for Time Machine? As a workaround,

2. I tried going back to Disk Utility to reformat the drive as an old-fashioned file system, but I can't figure out how. Selecting either volume and choosing Erase only gives me APFS options. Unlike in the old file system style, I can't select the 'parent' hard drive containing the volumes to start all over again. How might I do so?

Thanks so much for your help :)

Time Machine seems to do better if you have a dedicated drive for this purpose, not shared with other data, partitions or volumes. Time Machine is great when it works, not so much when it doesn't.

Backup disks you can use with Time Machine - Apple Support

https://support.apple.com/en-us/HT202784

Types of disks you can use with Time Machine on Mac - Apple ...

https://support.apple.com/en-au/guide/mac-help/mh15139/mac

How to use Time Machine to back up or restore your Mac:

https://support.apple.com/en-us/HT201250

3-2-1 Backup Strategy: three copies of your data, two different methods, and one offsite.