I have not tried either myself, but I wanted to mention that Versity S3 Gateway looks good too.
https://github.com/versity/versitygw
I am also curious how Ceph S3 gateway compares to all of these.
I'd be curious to know how versitygw compares to rclone serve S3.
When I was there, DigitalOcean was writing a complete replacement for the Ceph S3 gateway because its performance under high concurrency was awful.
They just completely swapped out the whole service from the stack and wrote one in Go because of how much better the concurrency management was, and Ceph's team and codebase C++ was too resistant to change.