I'm currently investigating Unity's (relatively) new Input System which intends to replace the Input Manager.
Of course, once you activate the new system, none of your old inputs will work in game. In fact, you'll get a bajillion errors in your console like this
InvalidOperationException: You are trying to read Input using the UnityEngine.Input class, but you have switched active Input handling to Input System package in Player Settings.
What's nice is you can now code using ENABLE_INPUT_SYSTEM and ENABLE_LEGACY_INPUT_MANAGER to ensure everyone plays nicely with each other!