Don't think anyone other than Strava and Komoot have sufficient user-generated trail database to be useful for your use-case.
Edit: hmmm I don't think I understand that wiki. Most of those are not the type of heatmap I was thinking of. I'll keep looking into it though.
Here's a link that has traces enabled (aka layer "G"): https://www.openstreetmap.org/#map=15/52.47166/13.40590&laye...
There's also a list of recent uploaded traces: https://www.openstreetmap.org/traces