How Do I Back Up Time Machine Backups?

Question: How do I back up Time Machine backups?
Why: Time Machine backups was on an external drive that failed.
What I did: I replaced the drive and restarted Time Machine on it. Wanting to not loose months of backups again, I tried copying Time Machine files to another new drive, but got an icon telling me “it ain’t gonna happen.”
The partition on the new target drive is formatted APFS Case-sensitive, which is the same as the current Time Machine drive. I tried Disk Utility > Restore with Time Machine drive as the source. Failed.
Time Machine backups are on an external drive, which will fail, and I can’t find a way to back them up.
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Ken Schuster