[Question] What’s the longest a sentient observer could survive in the Dark Era?

Periodically I look at this graph, and I’m like, “holy shit, that is so much Nothing. Wut. Like, they converted it to log-scale so it would fit into my brain and it’s still so much Nothing, Jezus Christ.

Eliezer’s Dath Ilan verse has this song for people who died before the invention of cryonics:

Even if the stars should die in heaven
Our sins can never be undone
No single death wil be forgiven
When fades at last the last lit sun.
Then in the cold and silent black
As light and matter end
We’ll have ourselves a last look back
And toast an absent friend.

And I find myself wondering “What are the physical limits on ’some sentient computation surviving into the dark era?” Assuming we don’t learn anything new about physics, or acausal-trade our way into another universe or whatever, what’s the farthest to the right on this timeline you could possibly get, if you goal was to have some computation that, as late as possible, looks around at the universe one last time, comprehends it, and says “yep, still full of infinite blackness. Goodbye, world.”

Vaguely relevant things I’m vaguely aware of include:

  1. Something something you can somehow harvest energy from black holes. Does this plausibly get us to the end of the Black Hole Era or is that energy eventually too weaksauce?

  2. Space is, like, really cold (especially when All Has Become Darkness), so any time-capsule robot would face an uphill battle not radiating it’s energy into the void.

  3. On long enough timescales, protons (probably?) decay, and… like, your robot would eventually… just… disintegrate?

If anyone knows enough physics to satisfy my random curiosity, uh, I’d appreciate it.