Doesn't ZeroSSL do this? acme.sh has been using it as the default for the last few years. As I understand it, it basically offers the same as Let's Encrypt.
The "ACME Certificates" are free and unlimited. The 3 free "ZeroSSL Certificates" are old-fashioned manual certs: this is a strictly more generous offering than Let's Encrypt!
> If you have a server or other device that requires automatic issuance of certificates and supports the ACME protocol, you can use our free 90-day ACME certificates on all plans.
Zerossl is integrated with Caddy by default and there’s no indication from Caddy that you would only be able to renew the cert twice before needing to cough up some money.