I did remove the ublock origin extension once.
Then I googled "ublock origin firefox" and installed it back again.
Well, I did disable and re-enable ublock a few times by clicking the big blue power icon.
(maybe that helped some lol.)
Then I just gave up on googling a solution.
Someone (StayTuned?) stated maybe Youtube is doing some changes to the platform.
So maybe Youtube fixed it on their end. And that's why it's back. (so I just had to wait and chill lol.)
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Today: I open a new tab in my Firefox (regular window, no private browsing).
Go to Youtube Home (youtube.com) signed in.
And Voila! The logo and hamburger button has magically re-appeared!!!
I am so happy it's back. I've missed you so much, youtube logo & hamburger button. (Don't ever leave me again.)
I'm mostly a lurker in the Computer forum, but I have to say this is the most entertaining thread I've seen in here. Thank you to all who made it happen.