You can submit a pull request with an override to https://pagure.io/ironthree/repochecker/blob/master/f/overrides.json -- if the format is not comprehensible, open an issue at https://pagure.io/ironthree/repochecker/issues instead.

I can add the necessary overrides myself. Does this look correct?

release: "rawhide"
architecture: "s390x"
package: "qcoro"
broken: ["cmake(Qt6Concurrent)", "cmake(Qt6Core)", "cmake(Qt6DBus)", "cmake(Qt6Test)", "cmake(Qt6Widgets)"]

Should I add this override for rawhide only, or for other releases too?

I can add the necessary overrides myself. Does this look correct?

Yes, but I think all packages using Qt 6 should have these.

Sure, do you want to compile a list so I can add them all?

Qt 6 is now available on s390x. This ticket can be closed.