TLS-ALPN-01 is the successor to TLS-SNI, and it has been in production at Let's Encrypt for some time now. https://community.letsencrypt.org/t/tls-alpn-validation-meth...

TLS-SNI has been disabled for almost a year for new issuances and the final nail in the coffin is to turn it off for renewals which is happening soon. https://community.letsencrypt.org/t/important-what-you-need-...