301 redirects and duplicate content

No. Why / where do you think there would be duplicate content? 301 is a permanent redirect - just a pointer to its replacement.

However if you have a lot of them from unrelated domains, like if you were buying a crap ton of domains with link equity solely to prop up another domain, Google may flag it as spam and either ignore those inbound links or slap you for it.

Yes its duplicate.

No it is not duplicate content.

301 is a permanent redirect. Google completely “forgets” anything that was on the old URL and looks at the redirect target instead.

It’s like moving and having your mail forwarded to your new address.

301 is redirect so not duplicate

Nobody asked for the definition of a 301 redirect. Please read the posts before replying.

You should read this on google.com.