Greywolf1965 wrote:
Is this new with Sequoia seeing that TM will format the drive to APFS. Can it be changed? I lost all my files that were stored outside of the backup files.
This is well documented by Apple.
Backup disks you can use with Time Machine - Apple Support
Back up your Mac with Time Machine - Apple Support
"Use your Time Machine backup disk only for Time Machine backups, not for storage of other files."
"Your Mac might ask if you want to erase the storage device so that it can be used for Time Machine. Either erase it or select a different backup disk or volume."
The requirement to use APFS for Time Machine backups is also explained in Apple's articles, the ones above as well as in others.