Although I did find the grayed Bing option, it was grayed because I was running without 'Internet Functionality' (top menu option).
I reset all to be on and when back on the main menu, all was OK :-)
However, now that I have reset all options to 'On', and I have re-booted (twice), my 'Manual cache' is again grayed out :-(
So, I think Microsoft is still VERY confused...!!!
Hopefully with the next update, tomorrow Tuesday 13 Nov 2020, things will get better.
If not, I will begin to regret buying MSFS2020 as well as a whole amount of hardware:
Full set of Thrustmaster full flight system, TCA clamp, Cougar etc....