Let me ask again a different way. How far is the Google mini from the cubboard where your router is?
It's possible that the cupboard location of your router it impactng the WiFi signal, especially if there are appliances between the router and your devices.
If smart steering is off that means you have a separate SSID for 2.4 GHz and 5 GHz. Which one is your Google mini connected to? Since your router is inside a cupboard the 2.4 GHz would likely be better.
So based on that information I have some comments and recommendations.
- The fact that the router is in the cupboard and the WiFi signal has to travel through the cupboard and another wall could very well be impacting connectivity. This is especially true if that wall is structural with pipes and heating ducts.
- You are using 2.4 GHz already which helps since it's better than 5 GHz at passing through solid objects.
- You have smart steering off which also helps because it prevents the device from fip-flopping between 5 Ghz and 2.4 GHz causing drops in connections.
- The remaining factor you can follow up on is whether the channel being used on the 2.4 GHz frequency is overcrowded. This could be the case if there are many access points from your neighbors. You may need to manually set the channel to one that is less crowed. See this thread which has a discussion on this topic: