RockyLinux is by the guy who did CentOS, and seeks to follow it's principles.
Scientific Linux is no longer a thing, essentially; from wikipedia:
> In April 2019, it was announced that feature development for Scientific Linux would be discontinued, but that maintenance will continue to be provided for the 6.x and 7.x releases through the end of their life cycles. Fermilab and CERN will utilize CentOS Stream[4] and AlmaLinux[5] for their deployment of 8.x release instead.
> RockyLinux is by the guy who did CentOS, and seeks to follow it's principles.
Not quite. Back in 2003, when folks were first coming up with the idea of creating a distro that matched RHEL as closely as possible, Greg Kurtzer (the Rocky founder) explicitly stated that he would be interested in helping host it, but that he was "totally not interested" in leading it.
Scientific Linux is no longer a thing, essentially; from wikipedia:
> In April 2019, it was announced that feature development for Scientific Linux would be discontinued, but that maintenance will continue to be provided for the 6.x and 7.x releases through the end of their life cycles. Fermilab and CERN will utilize CentOS Stream[4] and AlmaLinux[5] for their deployment of 8.x release instead.