Uptime Kuma supports certificate expiry notifications and will send you messages in whatever channel (e.g. e-mail, Slack, ...) you configure ahead of time: https://uptimekuma.org/

That way, even if some of your automation is borked (or if you don't have any), you'll at least be reminded.

Though with this being pushed, feels like nobody will have much choice, but automate: https://www.digicert.com/blog/tls-certificate-lifetimes-will...