Users who are not on Windows should use mono 5.10 or above. Previously any version 5 would do.
Most distributions that went to mono v5 at all should be fine. You can run mono --version to check.
https://repology.org/project/mono/versions gives a nice compilation of versions for distros.
Windows is quite good at updating .NET Framework, so the move to 4.7.1 from 4.6.2 should be fine.