CertbotCertbot is EFF's tool to obtain certs from Let's Encrypt and (optionally) auto-enable HTTPS on your server. It can also act as a client for any other CA that uses the ACME protocol.
Acme.shA pure Unix shell script implementing ACME client protocol
ACMECertPHP client library for Let's Encrypt (ACME v2 - RFC 8555)
ght-acme.shShell script to sign certificate by the letsencrypt CA
yaacYet another ACME client: a decoupled LetsEncrypt client
letsencrypt-manual-hookAllows you to use dehydrated (a Let's Encrypt/Acme Client) and DNS challenge response with a DNS provider that requires manual intervention
acmedACME (RFC 8555) client daemon
tipiTipi - the All-in-one Web Server for Ruby Apps