Did you solve your problem? I had a similar problem, but using an Ethernet gateway, until I discovered that my sketch was not using the 2.x API, contrary to the gateway. This is also the case for the BinarySwitchSleepSensor you mention. You might want to try with a sketch based on the last one on this page (using the 'initialValueSent' variable): https://www.home-assistant.io/integrations/sensor.mysensors/#mysensors-2x-example-sketch
After updating to the 2.x API, my sensor showed up in the entities list of Home Asisstant (v0.106.6, HassOS 3.12, on Raspberry Pi 3) and I could create a UI card for it.

(For some reason the entity is read-only in Hass.)