What I've seen so far:

• Shock Level 5: Big Worlds and Modal Realism
• What Are Probabilities, Anyway?
• Abnormal cryonics
• Cryonics without freezers: resurrection possibilities in a Big World
• The map of quantum (big world) immortality
• Comment by Wei Dai in 2019
• The Moral Status of Independent Identical Copies
• The Anthropic Trilemma
• Where do selfish values come from?

Maybe I should also revisit material on UDT/FDT/LDT, mathematical universe, and many-worlds.

Also check on Google for "magical reality fluid site:lesswrong.com" (ex.: this, this, this, this, this, this, this, this, and more!)

EtA:

• check out the bibliography of Digital Immortality: Theory and Protocol for Indirect Mind Uploading

And this Facebook group: Modal immortality

What else?

EtA: Anthropics also seem relevant. Ex.:

• (haven't read yet) Anthropics without Reference Classes

I recommend Forever and Again: Necessary Conditions for “Quantum Immortality” and its Practical Implications by Alexey Turchin. I don’t endorse everything in there (especially not the usage of “Time” in the x-axis of Figure 3, the assumption that there is such a thing as a “correct” theory of personal identity, and the claim that there is a risk of “losing something important about one’s own existence” when using a teletransporter) but it is one of the articles most relevant to modal immortality that I’ve found in the bibliography of Digital Immortality: Theory and Protocol for Indirect Mind Uploading, which you mentioned in your answer (and, for that matter, one of the articles most relevant to modal immortality I’ve found anywhere), and it is fairly thorough.