"For those struggling or preferred the key mapping of the 2.7X to 2.82 series of Blender, there is a way to bring back the shortcuts that we were so familiar with.

Options:
1) After an update and on the first launch of Blender, you can set up Blender to use the old key mapping from the Splash Screen.

2) If you missed that , you can reset Blender to think it's launching for the first time by deleting the 2.83 folder in your AppData\Roaming\Blender Foundation\Blender Folder then relaunch Blender and make your choices on the Splash Screen.

OR

3) But if you missed the initial setting in Option 1, you don't have to do Option 2. all you have to do is go to Preferences - KeyMap and change the Key Binding to the flavour you prefer."