Time Machine Disk Problems with Big Sur

I have encountered problems with backing up since upgrading to Big Sur (11.0.1).

1. Time Capsule on Airport Extreme could not backup. Warning popped up. I tried numerous things, including running disk utilities and erasing the disk and starting afresh. That did not allow me to back up. I presumed the Airport disk was dead.
2. I bought a WD external powered hard drive. I tried backup, and Time Machine requested that the disk be erased first before it could be used. After 3-4 hours of trying to make it work, and another 1.5 hours on the phone with WD, the following would happen:
   1. 1. Disk, after reformatting, will briefly show all permissions available (w/r, read only, me, everyone, etc)
      2. Within a minute or two disk permissions changed to "you have custom access" with no ability to select read-write
      3. The drive would then become "you can only read". Permissions for the drive were not changeable. I returned the drive, presuming it is faulty.
3. I ordered a Seagate drive, after vowing to stay away from WD. The exact same problem is occurring again. Time Machine asked for the disk to be erased first. It then became a read only disk and Time Machine itself could not access it.

Time machine can never begin to write to the disks. It just gets stuck in "preparing backup ..." for hours. I have let it run as long as overnight, and it does not write to the disks.

So ... the same problem is being experience by three different drives (Airport with build-in 3TB drive, WD 8TB drive, and Seagate 8TB drive).

Preferences > Security & Privacy > Full Disk Access and Files and Folders have not disabled access to the drive.

I have tried formatting the disks in all available formats (APFS), which no longer include OS Journaled, also to no avail. The only options are those screenshot below.

Mac has been rebooted with PRAM also reset. Disk Utilities has run on the build-in drive.

Much appreciate help on how to make this work.