Don't know if this is well-known, but I found out a cool thing for old #Garmin devices, which are no longer supported:
You can download #openstreetmap data for Garmin and place it on an FAT formatted SD-card. File structure should look like this:
SDCard/GARMIN/gmapsupp.img
Your device now detects the new map. Tested it with a 2010 #BMW nüvi 715 and routing, simulation and POI seem to work. Just had to reduce level of detail to low.
Backup your old map before!
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