Sorry to the OCaml hacker using Compiler Explorer for the late update (it took some time to deploy the infrastructure, etc.), but it now supports OCaml 4.12.0, but also 4.10.2 and 4.11.2!
4.12.0 flambda is still in progress. It should be available around next week.
Today we deployed 4.12.0 flambda. It must already be available!