RetroBar is a free program that brings the classic taskbar to Windows 10 and Windows 11. Not only that, but it provides the old layout as well.
Setting up is pretty simple. It's a standalone program. No need to install or anything. Though you may need .NET Core 3.1. But don't worry if you don't have that, the error that appears will take you to the download page.
You configure this program using the taskbar settings (right-click the taskbar) instead of using some config file or settings app, which feels quite natural. You have several taskbars to choose from, all from earlier versions of Windows. However, you cannot choose Windows 7, which is a real shame.
This program is compatiable with other classic taskbar/start menu programs such as Classic Shell. However, due to the smaller size of the taskbar, Classic Shell's start menu floats... unless you enable small taskbar buttons in the taskbar settings (or the registry in the case of Windows 11)
This start menu replacement is overall pretty good and true to the older versions of Windows that it replicates. However, you do lose some functionality that came as a result of newer taskbars - the show desktop button and the ability to peek at apps without switching to them. Still looks much better than putting a Windows XP start button on a Windows 10 taskbar.
You can download RetroBar here