I have one Kindle Fire using the Fully Kiosk Browser and a wall mount with a hidden power cord (https://a.co/d/05GVxVP). It uses the camera to turn on when you walk up to it. It’s ok, but I installed it 3 years ago and never really finished making a dashboard for it. In practice, we control the vast majority of stuff by voice with the Google/Nest Home integration, or switches. The big control panel thing doesn’t hold enough interest to even bother putting controls on it, and I mainly leave it showing air quality graphs.
Of more practical use are smaller panels for area-specific uses. I mainly standardized on NSPanel, because I was experimenting with them and ended up with a bunch. Example: https://youtu.be/DBzg7v1Q5Zo. I have a short attention span and tend to stop when it’s 90% good enough. I also have in other places a DIY HA SwitchPlate, and HASPone on a Lanbon L8.
The way I use them is to reflash the firmware with ESPHome, at which point they have nothing to do with Sonoff. I got really into these things when they came out and made a video about the process: https://youtu.be/Kdf6W_Ied4o?si=4nh7kP28IglwVHBx. There are a bunch of different ways to use them including retaining the original software, but I kind of stopped paying attention when I got mine working.
It's worth noting that they have two different products. The "NSPanel Pro" is completely different, I think it runs Android. I haven't played with that at all.