Garmin · On connect.garmin.com, open the activity → ⚙ gear icon → Export Original (.fit) or Export to GPX.
Strava · On strava.com in a browser, open your activity → ⋯ menu → Export GPX.
COROS · In the COROS app, open the activity → share icon → Export data → .fit or .gpx.
Polar · On flow.polar.com, open the training session → ⋯ → Export session → GPX or TCX.
Apple Watch · Let the free Strava app sync your workout, then export it from strava.com as above.
On Android, install RyannPace (browser menu → Add to Home screen) and you can share a file straight into it from your Files app.