* certbot - probably the mentioned python software
* ACME - the protocol, which had a change in the supported challenges
Also there are alternatives for all three points. There are other CAs implementing ACME, there are other ACME clients and there are still CAs supporting the old 'send an email and click a link' domain validation.
* Let's Encrypt - the actual CA
* certbot - probably the mentioned python software
* ACME - the protocol, which had a change in the supported challenges
Also there are alternatives for all three points. There are other CAs implementing ACME, there are other ACME clients and there are still CAs supporting the old 'send an email and click a link' domain validation.