I just went down a rabbit hole to remove the "Discover" button in Edge (top-right corner):
- `regedit`
- go to `HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft`
- add a key (folder) `Edge` (ignore the folder `MicrosoftEdge` if it exists)
- in `Edge` folder, add a `DWORD` with name `HubsSidebarEnabled` and a value of `0`.
- in Edge, go to `edge://policy` and click on `Reload Policies`
- it should list the policy and the 'Discover' button should disappear
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