I’ve just added a On/Off Switch in Smart Bulb mode to Apple Home, but it’s only populating as an Outlet, so I can’t use the Switch functions.
I’ve tried Factory Resetting it, and Dropping it out of Smart Bulb mode.
I have a bunch of White On/Off switches, and mine I added to Home Assistant, and then exposed groups to Apple (via a HomeKit Bridge integration in Home Assistant). So I’m not sure if my use case will result in the same or different behavior…
For me, in the Apple Home app, if I long press on a Switch, and then choose “Accessory Settings”, Apple gives me the option of “Display As” either Fan, Light, Outlet.
So maybe see if it works the same for you with the direct add into HomeKit.
As a starting point, see this like: White On/Off Switches recognized as outlets - #2 by jvm33 for how to make the switch appear as a light.
As a point of clarification, “Smart Bulb” mode means that power is always sent to the load (i.e., the ‘Smart” bulbs will always have power which is needed to maintain their network connections). The switch will still report itself to iOS home as being “on” or “off”, but it really isn’t changing the power output - power is always on. What you will need to do in Smart bulb mode is to set up automations to respond to the On / Off state reports from the switch to trigger your automations and, in those automations, you have to control the bulbs directly. Is that what you are trying to do?