In this post, Roko makes some simple estimates to conclude that there are not really any physical/material constraints on humanities' growth until about 10 trillion people.
Personal rumbling
That paints a different view of the future than I had in mind intuitively. Perhaps humanity could mostly solve resource scarcity within ~50-100 years and allow for rapid population growth (say, enforced by local governments for some reason [like trying to game global democracy, if I'm already painting one specific and weird future]). This type of thinking might put a big value on the not-so-far future, which potentially could be addressed by interventions other than advocated for in longtermism (say, advocate for medium-term (~100 years) contracts/policies, something about global warming, improved population policies).
That's great, thank you!
I've found this review (2015) of "critical metals" - roughly, those metals that are most needed and we'd likely to see a short in supply. And this recent review (2020) of studies on likely future (2050) demand for these metals. I'm not that sure whether these would be crucial in their impact on economic growth, even if they'd have limited supply; What would be the problem of having fewer jet engines?
Regarding solar energy, I haven't checked the calculations or extrapolated to the future, but taking a look at this I feel optimistic. They say that the Sahara dessert, for example, would be enough space to supply energy to the whole world 20 times over (although they didn't take into account loss of energy in transition and naturally it's not that practical).
I'd love it if someone would take a deeper dive into this topic. Toby Ord talks a bit about related issues of resource scarcity in The Precipice (Chapter 4, "Anthropogenic Risks", Section "Environmental Damage") and also thinks further research is needed (from an x-risk point of view, though).