Where do I find the file?
You need the activity you recorded, not a planned route: they are two different things, and only the first holds the trace of where you actually went.
Komoot
You can do it straight from the app, phone included.
Garmin Connect
From the browser, not the app — a phone browser is fine.
If your app syncs with Strava, go through Strava
Almost every watch and almost every app sends outings to Strava. In that case you don’t need the file at all: connect Strava and pick the activity from a list.
Connect StravaThe other platforms
We haven’t tested the steps for these ourselves, so we don’t invent them: here is where to download from, and the rule that works everywhere.
Suunto
From the website, opening the activity.
Polar
From Polar Flow, opening the session.
TrainingPeaks
From the website, opening the workout.
Wahoo, Coros and other watches
If their app can’t export, the outing is almost always already synced somewhere else: take the file from there, or connect Strava.
Relive
The activity usually comes from another app: take the file from the original source, not from Relive.
The rule that always works
Look for “Export”, “Download GPX” or “Download” in the activity menu — usually behind the three dots. If the app doesn’t have it, the same app’s website almost always does: open it in a browser, a phone browser is fine. We read GPX, FIT and TCX: if you get to choose, take the FIT, which carries more data.