I was trying to install dotnet 5 template for UnoApp and even though it worked on one machine other one seems to just print a list of current templates when I use
dotnet new --install Uno.ProjectTemplates.Dotnet::3.5.0-dev.270
command. I use the same OS on both machines (windows 10) and also the same version of dotnet (5.0.301)
Installing the Uno Platform templates is generally done through the Visual Studio extension, and can also be done through the dotnet new templates:
dotnet new -i Uno.ProjectTemplates.Dotnet
The command line you use is installing a pretty old version of preview templates. This one installs the latest stable.