Can time machine backup from external hard drives to other external hard drive

I don't know how your equipment was listed as Windows, and I did not even see that.

I used the MyBook as an example because it is a popular add-on external drive, and for no other reason.

PROVIDED you ERASED each new Drive with Disk Utility, by its immutable manufacturer-given device-name, and did not just install the drive-maker's Utilities and create a new Mac Volume on a NTFS drive, your external drives will be backed up by Time machine by default. if any external drives are still NTFS format drives, Time Machine will IGNORE them.

This is an important distinction, and Time Machine does not provide any error messages for any NTFS drives it encounters, but they are NOT backed up -- despite that you may have MANY Mac files stored on them.

I dunno what you are talking about.

Time Machine backs up your COMPUTER, including every Mac-format drive you have connected to it, unless you deliberately exclude a particular Drive or Directory.

HOWEVER: Drives like the MyBook came with software, and the manufacturer suggested you install that software.

What that software does is to "spare you the annoyance of having to re-initialize the drive" from its factory set Windows New Technology File System (NTFS, the W is silent because there are no other Operating Systems) or similar unusual (on a Mac) format. Instead, the software they provided would simulate a MacOS drive inside an NTFS file for your Mac. This is called a sparse bundle disk image.

Windows drives are NOT backed up up automatically!

The downside of using the manufacturer's software is that if the manufacturer's software is not loaded, the Macintosh Volume may not be readable, or may not be writable. This means that in startup manager, Installer, and in Recovery such as after a data loss, the Macintosh Volume may not be visible.

The standard advice given here to all users, including novice users, is to discard the manufacturers software and NEVER use it. "Best Practice" is to erase the physical device when new, using only MacOS Disk Utility, and create the fundamental data structures needed for consistent, reliable use by MacOS.

some drives com formatted from the factory in Windows

Leffy38 Said:

"Can time machine backup from external hard drives to other external hard drive"

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See if this applies...

Backing Up a Time Backing Backup of its Own:

If you wanted to back up Time Machine Backups to another drive, then Archive these.

Try Drag & Drop:

Im not so certain you can with APFS. But, if you want to back up a Time Machine Backup, then you'd have to plug both hard drives in to the computer > compress these to a new into a folder > and then Drag & Drop it to this external drive.

How to Compress:

Thing is, you'd have to place them back on this original drive informer to use them. If the original drive wen dead, then you might be out of luck. So, elevate whichever one you want > right click > select Compress. then Drag & Drop to the other hard drive.