To give a “recipient’s perspective” on the second email:
It does now say which domain name and which IP address were affected (which is good), but crucially doesn’t say whether the same challenge will be attempted next time. In my case I got an email for one domain that I don’t believe will fail (I’ve just tried dry-run and it says it could renew using http-01) and didn’t (yet) for one that I believe will fail next time (it did tls_sni_01 last time and dry-run fails for all challenge types).
Perhaps if there’s a “third email” it should explicitly suggest dry-run as a way of checking? Of course, assuming people are checking for renewals regularly they should get 30 days notice of a problem when a renewal fails.
The harder problem to solve is explaining to people what they need to do next once they’ve found (e.g. by a renewal dry run) that they do have a problem. The email does link to this help site; there’s lots of information here but maybe encourage people to post “solved problems” here too (e.g. “I was previously using tls_sni on XYZ server and I fixed it by doing A, B and C”).