Floorp, a Firefox Fork with an awful name, has moved some components inside a private submodule.

See also https://forum.endeavouros.com/t/floorp-going-closed-source/52783

Edit: They claim they will make that part open source too, eventually, and it is due to behavior of another browser: https://github.com/Floorp-Projects/Floorp-core/issues/62

Edit 2: They just open sourced the private repository 7 minutes ago, 2024-03-24T12:39Z