MacOS El Capitan installed on external drive - is it possible to transfer it back to my iMac’s internal drive?

I was trying to factory reset a 2011 iMac and due to other technical problems I almost bricked it. The only solution was to use a Time Machine backup from another iMac (same specs) and install that onto a separate external drive. Now the iMac won’t work without the external drive plugged in , and I can’t use the external drive for anything else.

Is it possible to transfer all data to the iMac drive ?

submitted by /u/NoNumbersForMe
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