I agree, likely the first immortal person has already been born. Perhaps even large swaths of the population are already effectively immortal, but they just don't know it yet.
Sadly, my main fear is that immortality will only be available to the extremely rich and powerful. Generally historical progress is made when the old guard die, be it in science with the leaders clamoring to old theories, dictatorships falling when their leader does, companies setting a new course when their founder/CEO retires.
I shudder at the thought of living in a world where everyone still dies like before, except an entrenched immortal powerful elite.
I feel like you and the parent need to give a better operational definition of what you mean by "practical purposes." The ultimate destiny of every bit of matter out there is to become part of a black hole, evaporate to Hawking radiation, then succumb to the expansion of space gradually putting every discrete particle outside of the future light cone of all others.
This should take unfathomably long epochs of time well beyond the current age of the universe, but it will still inevitably happen. This is even putting aside possibilities like proton decay and false vacuum collapse.
Don't get me wrong. Given the choice between a 100 year lifespan and a quadrillion year lifespan, my first instinct is to take the quadrillion year lifespan, but even then, it seems like you're incurring the very real risk that you'll eventually remain "alive" but in complete isolation with no matter to interact with that isn't part of your body, waiting for thousands of times longer then the Milky Way will exist for the attraction of a supermassive black hole to finally pull you in and end it. Given whatever sort of brain you might have has to have a finite storage capacity for information, you also open up the possibility that you'll spend the last few trillion years of your life with no memories except that complete isolation and experience of utter nothingness.
These are all sci-fi scenarios and there is no way to know for sure what will actually happen or what it will be like, but we do know for sure that a functionally immortal being would not just be living a normal life doing things animals typically enjoy doing, but forever. There are plenty of possible fates worse than death.
I feel like the situation you describe is fairly unrealistic because you'd definitely use simulations to pass time. And I don't see any reason why you'd be the only immortal being left, either.
All medical technology is maybe "available", but if you google "person dies from not being able to afford insulin", we can see that availability is only half the equation. It has to be affordable, too.
Sadly, my main fear is that immortality will only be available to the extremely rich and powerful. Generally historical progress is made when the old guard die, be it in science with the leaders clamoring to old theories, dictatorships falling when their leader does, companies setting a new course when their founder/CEO retires.
I shudder at the thought of living in a world where everyone still dies like before, except an entrenched immortal powerful elite.