In my project there is a custom server, that gives maps layers in WMTS protocol. As far as it's custom, it cannot send layers in TPK (ArcGIS extension pac ) format. Does iOS default Map KIT work with WMTS layers and how? Or does a third-party solution exists? Thanks in advance.
No it does not natively. You can use an library called Route Me on github. It is a BSD license. https://github.com/Alpstein/route-me