Despite using Tokio underneath, I think that Actix does NOT do work stealing and uses mostly separate threads:
Given this architecture, I think the article might inaccurate when it says that Actix handlers must be Send + Sync. See also: https://www.reddit.com/r/rust/comments/14cbe1u/why_does_actixwebs_handler_not_require_send/
Actix is a bit weird, but it has been around, and used in production, for a relatively long time.
I bought my Fairphone for similar reasons to you.
I had a second hand mid-range Samsung for about 6 months and then the USB port got destroyed. I was unable to replace the USB port so the phone is useless.
I bought a Fairphone 5 thinking that, if anything similar happened, I would NOT need to replace the phone and would save money in the long term.
Kids not dying in cobalt mines is also a bonus: https://www.npr.org/sections/goatsandsoda/2023/02/01/1152893248/red-cobalt-congo-drc-mining-siddharth-kara