Bumper has only side and indicators, no brake lights.
You should have something either side or from one of the four lamps? They are individually earthed back but can't remember a common earthing point but that would be my first place of inquiry as to a common shared earth corroded as I doubt you will have lost both sides and indicators at the same time with fuses?
And yes the bumper lights were added as it was recognized as a need to maintain position lights when the rear door was opened, I can quote my MOT cert as saying that I must have a warning triangle out in the road when loading or unloading my vehicle, this is due to position side lights being obscured by the spare on the rear door when opened.