People using the application will see the new name in U.S., but will see Lake Ontario in Canada. Outside of North America, users will see both names for the lake.
OSM is not really a map app, it’s a collaborative geo database. You can build apps of top of it, there are many many such apps. The https://openstreetmap.org/ website isn’t really a map app and is mainly tailored for the needs of OSM contributors and editors.
CoMaps is a map app that uses OSM data, and packages it in a nice, offline-first, private, and Open Source app that is quite good and easy to use.
https://cartes.app/ is another app that uses OSM data, but works closer to your regular maps, being online-first, which has its pros and cons. Still quite private and Open Source though.
OSM is not really a map app, it’s a collaborative geo database. You can build apps of top of it, there are many many such apps. The https://openstreetmap.org/ website isn’t really a map app and is mainly tailored for the needs of OSM contributors and editors.
CoMaps is a map app that uses OSM data, and packages it in a nice, offline-first, private, and Open Source app that is quite good and easy to use.
https://cartes.app/ is another app that uses OSM data, but works closer to your regular maps, being online-first, which has its pros and cons. Still quite private and Open Source though.