.NET Framework 3.5 is fairly old and hasn't been upgraded since 2010, so it conflicts with our corporate policies that dictate we cannot install products that are not updated to the latest releases and security bulletins issued by Microsoft. Can we use OpenBuildings Designer without .NET Framework 3.5 installed? If not, are there any plans to upgrade OpenBuildings Designer so that it only requires the latest release of .NET Framework 4.x for use with Windows 10?
Unfortunately no, we cannot change the underlying requirements for OpenBuildings Designer at this time. As per the readme, both .NET 3.5 and .NET 4.6.2 are required for various functionality available within the product: https://docs.bentley.com/LiveContent/web/Designer%20Readme-v1/en/GUID-4B3DBA9D-9B7C-4DE1-99C5-617E989FB6DE.html
Despite the "age difference" between .NET Framework 3.5 and Windows 10, Microsoft does support this combination. As noted on this web page, mainstream support for .NET Framework 3.5 SP1 ends in 2023 and extended support in 2028: https://support.microsoft.com/en-us/lifecycle/search/548 Bentley Systems is looking into long-term solutions to address our reliance on .NET Framework 3.5 to fall within the timeframes dictated by Microsoft.
Also see: https://docs.microsoft.com/en-us/dotnet/framework/install/dotnet-35-windows-10?redirectedfrom=MSDN