About the "No force feedback vibration in DirectInput games" section. Potential alternative solution would be to use "Xidi" wrapper on the game if required (Link: https://github.com/samuelgr/Xidi). From personal testing (tested rFactor 2 game; installer did not fix the issue; manual Registry Editing also didn't help), the wrapper successfully fixed the support of the gamepad for the game, and also allowed to experience proper Force Feedback and adjust the overall feeling. So I think it could be added as an alternative solution, but it would be per-game basis.
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