Isn't DNSSEC pretty much required for email deliverability?

No.

For additional info, see https://sockpuppet.org/stuff/dnssec-qa.html and https://sockpuppet.org/blog/2015/01/15/against-dnssec/

Those do not mention anything about email.

Since almost nobody uses DNSSEC and mail is delivered anywhere. No need to mention it in the articles.

So why link me irrelevant articles instead of saying that when I asked about email?

I was thinking that the article addresses the general, overall, technical aspects of a DNSSEC-less internet, that by its absence of any mention of email difficulty, that would address the question. That was my thinking.

DNSSEC adoption across the Tranco top 1000 is very low, and DNSSEC adoption in North America has fallen recently. Deliverability is a function of multiple signals, and I don't doubt the C.W. that DNSSEC is one of those signals, but it's obviously not a requirement, since nobody is doing it.