Can I use Time Machine to backup other external memories connected to the MAC?

I would like to backup the system itself, ...

Time Machine no longer backs up recent versions of macOS itself. If you are using an M2 MacBook Air then you are using one of those more recent versions.

Since macOS itself is no longer backed up, the only way to "restore" macOS is to reinstall it: How to reinstall macOS - Apple Support

... and this external hard disk drive.

By default, Time Machine backs up all mounted volumes with the exception of the Time Machine volume itself. In other words, if that external hard disk drive is mounted when Time Machine runs, then it will be backed up along with everything else not in Time Machine's exclusions list. The Time Machine backup volume itself is automatically added to that list.

For reference: Back up your files with Time Machine on Mac - Apple Support

It depends on what format the volume is in. Open the Time Machine area of System Preferences or System Settings and see if you can remove it from the exclusion list.

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