Nowadays you can get virtually unlimited 90-day certs from ZeroSSL if you use ACME through the EAB feature rather than using their API.

But their ACME support seems half-hearted at best. The endpoints often return errors for no reason, compatibility with clients is hit-and-miss, and they keep spamming you with renewal notices even if you renew the cert. For important domains these days I just get a cheap 1-year DV cert like the good ol' days.