Controlling over 4G/LTE

I’m going to build a drone using PX4 as heart and RPi with LTE as companion computer.
I read from the documentation that I will be able to control the drone using the QGroundControl application and receive video from multiple cameras on my android phone or PC via Zerotier service and control it with a bluetooth Android controller (please confirm everything).

As you know, 4G connectivity is payable. In my country it is €10 for 5GB. 720p transmission for an hour uses about 2GB or something (1GB RPi and 1GB Android on the ground). Is there any solution to flying at close range (500m?) for free?

I suspect that it is possible to connect via Android and RPi through the built-in WiFi module. If so, is it possible to switch to LTE during the flight, and the other way while catching back WiFi coverage? And what will the range and video quality be?

There is a nice device on the market - “Herelink HD Video Transmission System”.
Is somewhere a cheaper option to create a similar long range WiFi bridge between the Android screen?

Please help me find a solution.

If you are talking about PX4 Flight Control Software you are in the wrong forum.

Thanks for answer. I don’t know what the difference is, I just noticed that the Android QGC app is more user-friendly. What about my questions if I used Mission Planner instead of QGC?

PX4 is Flight Control firmware, Ardupilot is Flight Control firmware. They are different, you are in the Ardupilot forum. QGC can be used for both although it’s the native Ground Control application for PX4. Mission Planner can be used with Ardupilot.

So is there any solution to my questions if I was using the Ardupilot firmware?

What you looking for does not make much difference with what flight controller firmware you are using, people are doing long range video transmission in different ways if you search and look thoroughly on this forum, PX4 also have a forum like this, improve your search game and you will find some suitable options

Thanks for not answering me at the beginning.
I read longer on the web as you sugest and found a better solution - Open.HD.