For the limited Fenix device this is probably all that is needed. For other devices which allow address or POI search you should add option
–index and the TYP file that comes with the zip file. Didn’t try it but this should work:
If you have mkgmap installed and unzipped osm_generic_new_tiles.zip the command shown in comment #2 should work.
(replace 4470 with the downloaded version)
See http://www.mkgmap.org.uk/download/mkgmap.html
Try other map providers, e.g. https://download.bbbike.org/
Lambertus’ service is nice when it works but very unstable since years and Lambertus is no longer active in the community. In my eyes it would be better if his page would be closed it’s a one-man-show.