Just recognized, that this is working, even when ,you think it’s not…
I always tryed to test the fitbit sensor, but you shouldn’t do that.
Just start your sleep, when you select FitBit as device.
But of cause follow the instruction of the developer and it will work very great.
And @jiri-urbandroid after I made the mistake written in the comment, the whole setting section “sleep” just disappeared.
I had to reset the app and restoring an Backup