Unity supports a modern .NET runtime. You may encounter the following issues when using the .NET runtime:
The stable scripting runtime comes with a larger .NET class library API than the legacy scripting runtime. This means the code size is frequently larger. This size increase may be significant, especially on size-constrained and Ahead-of-Time (AOT) platforms.
To mitigate code size increases:
Modern Mono has TLS 1.2 support for a number of platforms. Unity supports TLS 1.0 in the .NET class libraries, and TLS only works for the Mac Standalone player. Where you require full TLS support, use UnityWebRequest or platform-specific native solutions. Unity is actively working on adding TLS 1.2 support for all .NET class library APIs on all platforms that Unity supports.