How to back up my back up disk to a 2nd external disk and exclude the HDD/SDD in the mac itself in OSX Ventura? The internal drive is not visible in the 'Exclude from backup' menu.

No longer possible to Backup a The Machine Backup Drive to another External Drive.

Not even possible to use a Third Party Cloning Software to Clone the TM Backup Drive to another External Drive

TM Backup Drives are in the APFS Drive format are are rendered by the Operating System as Read Only

Beside, TM Backup since macOS 10.15 does not include at Full, Complete, Functional Working copy of the Operating System

It will only backup the contents of the User Account ( Home Folder ) of this machine.

Just connect two backup drives. It will backup to both and you will have two backups.

You could try another backup solution to backup your backup drive, but it would be a way better idea to back up your Mac with that other backup software.

It was never a good idea to do it before. Time Machine isn't designed to make a backup of its own backup.

The old HFS+ backups were essentially a duplicate of the Mac, so backing that up would probably result in the same thing, but you would have to somehow restore that backup, then restore for the restore.

The APFS backup isn't configured the same, so backing it up would probably not work at all.

Was looking for a specific link on Cloning a TMBackup and finally found it

refer to below link from the Developers of Carbon Copy Cloner

https://bombich.com/kb/ccc6/can-i-use-carbon-copy-cloner-clone-time-machine-backup

Welcome and the alternative seems to be the better choice - Two different External Drives

Welcome

Yes experience can be great teacher

Rescue Plan I have been using for years now , 3-2-1

3 Backups using 2 different methods and 1 Off Site incase of Natural or Un-Natural Disasters