Either way it's not a "standard OSM app", just a popular one.

You're absolutely right, I was thinking of osmAnd, maybe I should have said biggest instead of standard, whatever thanks for your correction

i cosider it the reference implementation

It isn't though. The Carto rendering style shown on openstreetmap.org is as close as we get to having a reference implementation. Osmand, while a good product, is much further removed from the OSM community.

Without getting into how official a product OSMAnd can be considered, I think it’s worth pointing out that Carto has limitations that OSMAnd improves on. Due to OSMAnd’s configurable vector drawing, it is possible to make the map show road surfaces or whether roads are lit. These are features missing from official OSM.org, which of course serves as little more than a tech demo.

Well, on iOS the app is free, but you can download a limited number of maps. Then it's either subscription or payment for individual regions. Maps.me or Google or Yandex maps have free downloads. Organic maps also claim not to track activity.

Yup... but it also helps to know that OSM is not a cheap surrogate for the above-mentioned commercial services, for hiking or cycling it's actually much better - at least as far as the map is concerned, the navigation features of the apps I tried until now are unfortunately a bit lacking.