Nice work on v1.3, the markdown export is a solid addition.
One feature idea, since you’re already tracking cert expiry per URL: might be worth also flagging domain expiry alongside it. A cert can be perfectly valid but the domain itself lapses (happens more often than people think), and that’s a blind spot most cert-monitoring tools don’t cover.
If you don’t want to build a full WHOIS parser from scratch, WhoisFreaks has an API that just returns expiration date + registrar info for a domain, could slot into your existing report loop pretty easily. Just a thought if you’re looking for what to add next.