DJI GO 4 App shows two icons: one with RC symbol with bars and another as "HD" letters with bars.
My understanding from User Manual is that there are TWO separate links between the AC and RC:

1. Remote Controller Signal
2. HD Video Link Signal

Touching the second icon brings the user to the HD Menu where the user can change from Dual to 2.4GHz or to 5.8GHz frequency.

But what about the first one?

I mean the Remote Controller Signal frequency. Can the user change it?

Hi, no it can not be changed.

Fly safely and enjoy
Alex

Hi, thanks for the inquiry. The signal on your remote controller can't be changed, however, the HD settings can be set 2.4 GHz or 5.8 GHz depending on your preference. You can also check our antenna tutorial for you to have a better signal on your RC.  Please see the tutorial below. Thank you for the support.

DJI Tony Posted at 11-7 13:35
Hi, thanks for the inquiry. The signal on your remote controller can't be changed, however, the HD settings can be set 2.4 GHz or 5.8 GHz depending on your preference. You can also check our antenna tutorial for you to have a better signal on your RC.  Please see the tutorial below. Thank you for the support.

https://www.youtube.com/watch?v=P7M9JtfVwQE

Thanks, Tony.
Understood.
I am also aware about the option switching the HD Video Link from Dual to 5.8GHz or 2.4GHz strictly.

The issue is that I recently observed the scenario when (at the certain distance) the indicator of HD Video Link showed all bars, whereas the RC Link indicator was blinking indicating a very unstable signal. At that time the HD Video Link was set to 2.4GHz strictly, so that my idea was to do the same (to set 2.4GHz) with the RC Link.

It looks like this is not possible. Sad.

Thank you.