Waymarked Trails does support the three-letter acronyms, but the developer isn’t a big fan of them: https://community.openstreetmap.org/t/bike-route-networks-classification-icn-ncn-rcn-and-lcn/121700/36

There’s longstanding desire for reforming recreational network tagging in the U.S. I’m a bit amused that it started with this trail of all things. The forum thread above is going around in circles, but one takeaway is that the hikers aren’t happy that cyclists coined cycle_network=* and left behind the hikers a second time.