Don't test for C++version, test for features

[mapron]

#if !(defined(_MSC_VER) && _MSC_VER >= 1910 && ((defined(_MSVC_LANG) && _MSVC_LANG > 201402)) || (__cplusplus > 201402))
#error "Library SUTFCPP requires a compiler that supports C++ 17!"
#endif

I found such a check in your code.
I think it's much better to check for library feature macros and compiler feature macros for what you exactly used.

I had a lot of problems in my past, checking for __cplusplus and then having issues in Linux, when compiler and STL version are not in sync (imagine using clang 10 with libstdc++6 for example).

[devatrun]

Completely agree with your comment. I also encountered this problem on Linux. Actually this guard was made only from the reason of complication. However, we have another problem, how to keep track of these flexible settings when the library changed.
I will take this into account and i will think about this problem.

[mapron]

About problem 'how to track' - yeah. If you don't used to tracking feature test macros and stuff, it is hard. But that thing make things way more portable. Bad things also can happen even if you a large company - google/googletest#3659