System.DllNotFoundException: ./x64/libSDL2-2.0.so.0

I’ve simple added reference to Monogame.Famework.dll (3.6 version) and application does not run

Critical application error: System.DllNotFoundException: ./x64/libSDL2-2.0.so.0
at (wrapper managed-to-native) Sdl:GetVersion (Sdl/Version&)
at Microsoft.Xna.Framework.SdlGamePlatform…ctor (Microsoft.Xna.Framework.Game game) [0x00033] in :0
at Microsoft.Xna.Framework.GamePlatform.PlatformCreate (Microsoft.Xna.Framework.Game game) [0x00000] in :0
at Microsoft.Xna.Framework.Game…ctor () [0x001fb] in :0
at Terminal.Payment.UI.MyGame…ctor () [0x00000] in /media/destructor/Documents/Projects/Terminal_Crossplatform_copy/GUI/Standard/TerminalUI/MyGame.cs:45
at Terminal.Payment.UI.Program.Main (System.String[] args) [0x000e1] in /media/destructor/Documents/Projects/Terminal_Crossplatform_copy/GUI/Standard/TerminalUI/Program.cs:41

And libSDL2-2.0.so.0 exists but not in ./x64/libSDL2-2.0.so.0 and in /x64/libSDL2-2.0.so.0 (without dot in path)

I solve problem by coping folder /x64 and /x86 to my application folder. But why is this folder not self coping?