Steps to reproduce:
NOTE: The repro steps in this bug ticket https://jira.unity3d.com/browse/UUM-114285 trigger the same underlying issue and are much simpler to repro

1. Create a new Unity project using the "Get Started With Unity" template
2. Observe the Editor

Actual results: Editor toolbar is missing

Expected results: Editor toolbar is seen at the top of the Editor

Reproducible with versions: 6000.3.0a2, 6000.3.0a3

Not reproducible with versions: 6000.1.14f1, 6000.2.0b11

Couldn't test with: 6000.3.0a1 (due to compilation errors)

Tested on (OS): Ubuntu 24.04

Notes:

• Does not reproduce on macOS Silicon Sequoia 15.5 or Windows 11
• The toolbar only seems to be missing after creating the Project, when the Editor is restarted, the toolbar appears
• Closing the "Tutorials" tab/window fixes the issue and brings back the Editor toolbar, however, opening the "Tutorials" tab/window again (Tutorials > Show Tutorials) makes the Editor toolbar disappear again
• The reason this occurs with the "Getting Started With Unity" template project is that the first time this project is loaded the Tutorials tab is automatically opened, which triggers the issue as described in the previous note.