I have retested this issue after the recipe was updated using Firefox Release 115.0 (Build ID: 20230629134642) and I can confirm that is no longer reproducible. The "Easy Setup" screen is successfully displayed if Firefox is pinned to the taskbar.
Bug 1842162 Comment 3 Edit History
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I have retested this issue after the recipe was updated using Firefox Release 115.0 (Build ID: 20230629134642) and I can confirm that is no longer reproducible. The "Easy Setup" screen is successfully displayed if Firefox is pinned to the taskbar. Considering this I think that we can close this issue.