@iain-niblock

For a cycle tour route in Italy, you can explore long-distance cycling routes available on biroto, which has a list of 27 official cycleways. All of these routes come with GPX files, making it easy for Garmin devices to access the routes ([1]).
You can specifically look into the EuroVelo 8 Mediterranean cycle route, which covers various regions of Italy. This route also provides GPS tracks for download, perfect for planning your cycling holidays ([2]). Access these GPX files through the respective websites to get them onto your Garmin device.
Let's look at alternatives: