What to do with duplicates?

Question

Search Engine Optimization

There is a site on the old Joomla, respectively, with duplicates of the main page (pieces 5-7).
The duplicates look like:
/index.php
/-url-url/46--url-url
and so on.
Previously, some of them have long been banned from indexing through ROBOTS.TXT. And some were indexed without any restrictions.
When transferring to another engine, the question arose: what is the best way to deal with duplicates after the transfer.
Do nothing to make them fly out of the index over time, since they will give a 404 error? Or redirect with a 301 redirect to the real home page?
What will be the opinions of the experts?

Answer 1

301, why lose customers with your 404?

Answer 2

use rel canonical
https://moz.com/learn/seo/duplicate-content