I note that physics is safe due to the expanding — or else contracting - universe. Any photons will eventually disperse to zero energy for our expanding universe, or heat towards Planck energies for a contracting one.

In both cases an event horizon will veil the apparent problem.

But more generally the photons wouldn’t agree with baryons on “the end of the universe” by way of relativity, each would observe the future according to its own coordinate frames. Not even photons would agree despite traveling at the ultimate speed limit. Photons encountering black holes would already seen the end of time at the center, but be reconstituted in Hawking radiation, et cetera.