I used to have an office slightly offset from the final approach path of the local airport with a window that gave an amazing view. I'd leave my airband scanner on as background noise while I worked in a very quiet, mid-covid office.
This info is in the automated weather broadcast (ATIS) audio for any towered airport.
Most large airports provide a textual version (D-ATIS), so suitably equipped pilots don't have to listen to it and scribble it down.
E.g. Heathrow now from random unofficial website: https://atis.guru/atis/EGLL
EGLL ARR ATIS T 1820Z LANDING RWY 27L…
EGLL DEP ATIS U 1427Z PILOTS ARE EXPECTED TO CHANGE TO RWY 27R AT AT 15:00 HOURS… DEPARTURE RWY 27L…
logifail•1h ago
Errm, what? "Not easily definable"? Based on what?
I've just opened FR24 and in less than one second I can tell that they're currently doing Westerly ops, which isn't a surprise.
Arrivals: 27L Departures: 27R
You don't need to "predict" what they're doing, you just need to look at where the aircraft lining up to land, and (on the other runway) where they're departing from.
(Full disclosure: have done many hundreds of LHR flights over the years...)