Hello all, after a couple of years I’ve tried again to make my own maps and I have been successful in getting them to appear on my Dakota 20. Its probably not the best way but it works for me. I download the .pbf file for the country or area I’m interested in from http://download.geofabrik.de/. I then split the .pbf file using the following command:

java -Xmx1024m -jar ../splitter/splitter.jar --max-nodes=900000 madagascar-latest.osm.pbf

Working from the example settings from https://wiki.openstreetmap.org/wiki/Mkgmap/help/How_to_create_a_map I then use the following command:

java -Xmx1024m -jar ../mkgmap/mkgmap.jar  --route --mapname=63240261  --add-pois-to-areas --bounds=../bounds-latest.zip --precomp-sea=../sea-latest.zip --index --country-name=MADAGASCAR --country-abbr=MD  --description="Madagascar OSM 07072022" --family-name="Madagascar OSM 07072022" --family-id=0261 --gmapsupp ./6324*.osm.pbf

Once finished I rename the gmapsupp.img file by appending the country abbreviation and then copy the file to the microSD card.

I though I would update on my progress just incase there are others still using their trusty Garmin devices!