Boot Fedora-Workstation-Live-43-1.4.x86_64.iso, on Welcome page click "change system keyboard layout", add an additional "Russian" Input source, come back to Welcome page, you will see "More than one layout is detected.Remove additional layouts to proceed." error message. Remove "English"and add "Russian" Input source, come back to Welcome page, "The selected layout does not support ASCII input. Please select a different layout to proceed." error message come up, and "Next" button is still gray.
Reproducible: Always
IMO webui should allow user choose more than one layout.