Each version of the UA .NET SDK supports different Frameworks and Security Policies. This table shows the supported compatibility between them.

UA SDK Support Overview

* Frameworks for which SDK assemblies are provided, and regulary tested. However, because of backward compatibility within .NET Frameworks, the assemblies may be used with Frameworks not listed here. For example, a Framework 4.5 assembly can also be used with Framework 4.6, 4.7, or 4.8 applications.

** These Security Policies are deprecated by the OPC Foundation, hence disabled by default on the server-side. Because of backward compatibility they can be activated by ServerSettings AllowDepreciatedPolicies.

Note: Due to backward compatibility, our .NET Framework 4.8 and both .NET Standard assemblies already offer compatibility with Microsoft's .NET 5.0 Framework. But we cannot provide any support for it.
Due to the Long Term Support (LTS) of .NET 6.0, we have decided to move directly to .NET 6.0 and skip .NET 5.0.
To avoid issues and incompatibilities, we recommend using .NET 6.0 instead of .NET 5.0.

Note: On Linux environments, .Net Core 3.1 CRL provides decryption issues with Certificates with a KeySize of 3072 Bit in combination with the Aes256Sha256RsaPss security policy.
To avoid issues use a 2048 Bit or 4096 Bit Certificate KeySize instead. Find more information about the issue #71607 on GitHub.