The custom maps community for wahoo is very strong. They update maps, and using OSM data, more frequently then wahoo. You can download maps here and then you push it to your device with an app called Elemantary. Find the read me in that onedrive folder.
Getting the bolt into dev mode such that it can connect via usb is a bit fiddly, you have to push power and up/down buttons at once. But if you are persistent you will get it.
Now having used Ridewithgps for planning I find it superior to Komoot. I find the yearly plan a bit expensive as I don’t use it often, but subbing to the monthly plan on occasion is a fair price imo. The free feature list also pretty rich already. So consider your use cases.
Maybe download something like Organic Maps on iPhone for offline maps as a back up solution.