My favoured online route planning site, bikehike.co.uk, recently suffered a licensing/API problem so I tried RWGPS (the free version) as I have an account and needed to plot some routes for a recent holiday in Scotland.
Pretty impressed TBH. There’s a recent review over on bikepacking.com and I think the comments there are pretty fair. Like a lot of route planning sites they use OSM mapping but unlike many they pull in updates on a regular basis so if you find something wrong it’s (relatively) easy to sort out by editing the base maps. I did this after our holiday where forestry access tracks were incorrectly classified as being pavement rather than “gravel”.