I am going to ask obvious questions, so bare with me and don't get mad. 🙂
You have reinstalled Photoshop and reset Preferences. (Reinstalling does not reset Preferences unless you use the cleaner tool. Come to think of it, it might come down to yet another reinstall, but use the Cleaner Tool between uninstalling and reinstalling, but hold in reserve for later.
So reset Preferences again, but do it manually.
https://helpx.adobe.com/ie/photoshop/using/preferences.html#Manually
Do you use custom workspaces? If yes, set and reset the Essentuals Workspace.
Are the default shortcuts there when you open Edit > Keyboard Shortcuts?
Do you have any plugins or extensions installed? Try opening Photoshop while holding down the Shift key. This forces only Photoshop to load.
What processes are running in the background, and could they be stealing focus for the shortcuts? This one is a stretch because of the global nature of the problem, But Nvidia Geforce will definitely overight some of Photoshop's shortcuts as a for instance
You have tried different keyboards, but whaty about keyboard drivers? I don't know this for a fact, but Photoshop does seem to hanndle some APIs differently to other apps. So do you have a gaming keyboard or mouse, for instance, and do you have an interface like Logitech G-Hub or Options, or Corsair iCue or Razer Synapse? I have used all of them and they can all lock out some functions, but IIRC it's usually with a key.
So good luck, and we await to hear how you get on.
My gut is that another reinstall, but this time using the Cleaner Tool is your best bet.
I think
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