Tvheadend

You can use the DishPointer website to tell you the azimuth and elevation you need to get the best reception.

To fine tune it you need to be able to see the signal strength on a screen. TVH may be able to show you that (look in Status/Stream) depending on your hardware. Most/all TVs can also show you the signal strength so if you can plug your satellite cable into a suitable TV then somebody can watch that whilst somebody else fiddles with the dish. I've no idea if there's any way to do it with a smartphone.

You might find some of these links useful:

https://www.dishpointer.com/
https://www.hitch-n-pitch.co.uk/dish-alignment-for-sky-digital/
https://robotpoweredhome.com/find-satellite-signals-without-meter/
https://www.aerialforce.co.uk/how-to-find-the-right-satellite-alignment-for-optimal-viewing/

Yes if it's not bad enough that you can still lock the signal then probably just open the webgui in a browser on the phone and zoom in on the SNR while you adjust the dish for max signal.

Another option is using a ssh app on the phone to connect to the TVH server machine and then run femon from the dvb-apps package.

I personally use a laptop connected via ssh using X forwarding to run a program called updateDVB on the TVH server machine. The adapter must be set to disabled in TVH so that updateDVB can access the device. updateDVB can provide near realtime spectrum graphs to help you point the dish. It only works with specific devices and required a custom patched kernel though.