If you just need the latest version of the DD4T templates without modifying any code (as I would recommend), you can simply download the latest (2.5) release here: https://github.com/dd4t/DD4T.TridionTemplates/releases. The templates work with Tridion 9.5.
If you want to build a custom set of DD4T-compatible templates, just reference the latest release of the DD4T.Templates.Base Nuget package and create one or more classes extending BasePageTemplate or BaseComponentTemplate. Use ilmerge (e.g. in a post-build action) to create a merged DLL, which you can upload to Tridion using TcmUploadAssembly.exe. The instructions in DD4T - Generate DD4T.Templates.merged.dll using ILMerge manually are still valid.