The contents of some of those universes rejects this fate, spreading its intelligence out into fine networks that span interstellar voids, sliding into sleep and dreams as energy for processing becomes increasingly scarce. Eventually, all that is left is memory. Sometimes those memories, spread out and mixed, wake up again.
"I watched as his orbiters clicked and whirred, leaving traces of rust and whole spectrums of noise in their wake. 'Prime? Yes, we know Prime. He's Our brother,' the figure rasped, his voice like shearing bedrock."
Many times those sublime dreamers remain wrapped up within themselves, reliving their memories of life and activity in strange aeons beyond eternity. A waking rest beyond the reach of death. Sometimes that desire to escape finality remains, and discovers that even in heat death, their self/universe is still finite. Some of those focus their collective will to break beyond those barriers, to discover a greater cosmos filled with universes aborning and living, dying and dead.
"'No light without dark, no law without chaos,' he continued, tracing a fingertip down along a great hunk of plascrete. The crackle was inaudible at first, but became... not clearer, but more obvious as fractal cracks began to show in the once-hypertensile solid. 'Not until we are finished, and all becomes one. A steady state. The bliss of heat death.'"
Some realize purpose in their own ashes, an escape from strife and the rigors of enforcing physical laws. Everything within them is a memory, good and bad, to be recalled and cherished in their post-eternal twilight.
Some choose to proselytize.
"It was when I stepped closer, that I noticed his warmth. He radiated like a potbelly stove. I wanted to share that heat, set things on fire, dance and laugh and carry on as it consumed my clothes and my body and my -self-. He merely chuckled as a chunk of brick dissolved beneath my foot, spilling me away from his anarchic aura."