Does that mean when HDR is not enabled in SDDM (plasma settings not exported to SDDM) or with a HDR enabled SDDM it is too bright and vivid. With the latter, with the breeze default I don’t think so (but that could be down to personal taste).
Maybe change the SDDM background image to something darker?
I don’t think it will be fixed until
comes out and the “old” SDDM basically gets replaced.