Band steering and a shared SSID can affect setup of things that do not use bluetooth but instead use the broadcast flood of specific sized ethernet frames to push over the wifi details and auth for the cloud server like older tuya stuff, as the phone will never sit on 2.4GHz for long enough for the device to see the transmissions.

I know that other implementations used broadcast frames to get the data across but that has other issues with most decent wifi kit which will turn it into unicast to devices instead of broadcast at the lowest rate.

But again, once set up there should be nothing stopping them from working on a mixed frequency network. Until you add in WPA3 which breaks many things.