On: Gimp 2.99.2 – GTK3 user interface toolkit

[maxerickson]

Netscape Navigator on Mac used it in 1999:

https://www.w3.org/WAI/UA/netscape-keyboard.html

I don't have a thought of where to check next. It could originate there, as a mnemonic for command+link.

[ziml77 → maxerickson]

It's "L" is because it focuses the location bar.