Today I managed to install .NET Framework 4.8 on my VM with Windows Vista Home Basic x64, how did I do it?
First to install it use the method previously used with the .NET Framework 4.6.2 and 4.7.x; nothing more than this time the procedure is longer since when starting any application designed for .NET Framework 4.x in Vista an error dialog appears for lack of instructions in kernel32.dll and ole32.dll respectively.
In HxD edit the clr.dll file that was the library that calls those instructions, replace clr.dll with the edited version and, surprise!
NET Framework 4.8 is compatible