I don't own a tablet. The app will load onto an IPhone but the user experience there is too miserable to be used. It was never my intent to use the app, as the promotional materials mentioned that it was possible to run KStars/Ekos remotely on the SMP using VNC, That is indeed the case. I have started the SMP and can connect to it through its hotspot, and then switch it to use my Wifi network. It comes up and I can start KStars/Ekos.

However, devices plugged into the power ports on the SMP are off, apparently by default. So nothing works. I need to turn them on. Supposedly, there is a screen for this in the app, but I see no way to accomplish this without using the app. Supposedly there is StellarMate Pro device in the INDI control panel. But I do not see it there. So I am stuck with devices I can't turn on. How may I get around this. Is the app the only way? Or am I missing something.

Figured it out myself. From my previous experience with Astroberry and AstroArch, I knew that the INDI configs were in /home/.indi. Edited the file SM Pro_config.xml in that directory to turn the first two power ports on and rebooting got my devices working. If there is a GUI way to do this, I haven't found it.

Did you check under the INDI (I think it is) interface where all your devices are listed?
I know with my Pegasus PowerBox, that is where the power controls for it are.

Jasem suggested creating a "remote" link ( a link to localhost:{port} ) as a way to make the SMPro itself to be seen as a device, and this got me going.