Hey Stephen,
You’ll have to tell me how you managed to get the slider to move in 18% increments as that was something I wasn’t able to do.
I ended up configuring the fan as a light in Local Tuya. Assign DP 3 (or whatever DP is the speed control in your device) as Brightness when adding the light control. Set Brightness Lower Value as 1 and Brightness Upper Value as 6. This will cause the brightness slider to control the speed. In my case, I set it from 1 to 5 and hence my brightness slider % to fan speed mappings work as follows:
Slider 1% = Speed 1
Slider 25% = Speed 2
Slider 50% = Speed 3
Slider 75% = Speed 4
Slider 100% = Speed 5
Yes, this makes your entity of the type “light” rather than “fan” but apart from this, it works perfectly. No hassles for me so far.
Hope this helps you out.