Let's Encrypt Is Down
letsencrypt.status.io
letsencrypt.status.io
Even if you obtain the self-signed cert out of band (and explicitly trust it), how do you authenticate that channel?
Self-signed certs are not scalable or particularly useful for internet users. Please don't recommend this.
If your 'lets encrypt' cert is not renewing on a chron job or something you are doing it wrong.
Every guide I've seen involves setting this up.