google maps/apple maps

I don't have apple products, so can't comment on that, but Google maps works fine anywhere you have WiFi. You can also download maps to use offline. Are you using this for city navigation or highway?

I use Copilot throughout Europe, which doesn’t eat into your data allowance.

You need to download the map. It's possible to download maps in Google Maps, but I don't know if you can download entire countries... or an continent.
In this case you can use something like Tomtom, which is the market leader in Europe as far as I know. Tomtom costs $20/year, and includes maps of all regions of the world + traffic alerts. For traffic alerts you need a data plan of course, but you can download all the needed maps at home.
Tomtom offers 50 free miles a month, so you could try the app before you go on holiday.

I use maps.me I don't like Google, everything is a washy shade of grey and not easy to see, and it doesn't show rail lines very well.
I find maps.me better for urban walking.

With maps.me, once you have downloaded the maps for an area, it doesn't need a phone data connection, it is like a normal Satnav (GPS receiver).
You can force it to download maps for an area before you leave (while you are still on WiFi) by calculating a route to somewhere, or panning the map to the desired area and zooming in..

Google Maps "offline" works without a data connection, if you download the map ahead of time. It's easy: go into settings and find "offline maps" and choose an area, then download it. (The map uses space on you device; the larger the map area you choose to download, the more space it requires.) Keep your phone on airplane mode then turn on WiFi (so you can use the phone at your hotel etc) and drive as needed. No traffic into, though, without a data connection.

To see how it works, try it at home first. Download your home area as the "offline" map and take a drive to test it out. It will work the same way in Europe except that things are in kilometers not miles.

Unless you have a locked phone, though, getting cheap data with a SIM card is pretty easy these days, however, and offers you other advantages (like traffic data when driving, also public transit and walking directions with Google Maps, which doesn't work "offline.").

another one for Maps.me that's what I use. Just download the country or town or area you need to your phone from their easy to use website. Then it's all offline directions. I delete the map when I get home and don't need that country map anymore.