I've been using the "L" key to jump ahead on YouTube, but as of this week pressing the key keeps opening the Firefox Search Bar instead. It's driving me nuts and I'm about ready to give up on FF. I can find no way to change the shortcuts or stop it from taking over when I use shortcuts on various sites. Any suggestions? Win10 Firefox 109.0 (64-bit)

I just tried to scroll forward in my video with the L key, it works for me. I also use Windows 10 just like you. Perhaps you are doing something wrong? I start the video and just press the letter L and it fast-forwards 10 seconds.

Ctrl+L is the keyboard shortcut to set focus to the location bar, so you may have a stuck Ctrl key.

Did you try to close and restart Firefox or reboot the computer ?

It is possible that some status keys have the wrong state and Firefox sees them as still pressed.

Try to press all the status keys (Shift, Ctrl, Alt) a few times to see if that helps to recover from this. If it doesn't help then close and restart Firefox or reboot the computer.