Is there an open-source smartphone that I can get when my iPhone ultimately fails?
Why? IPhones are now being assembled in Indonesia, Vietnam, Brazil, and India, as well as China. There are no forced labor workers or underage workers being used on making Apple products. This is propaganda using Apple as a convenient target.
Some of the cheap phones are better than before, and nifty VPN apps are available. Nothing like a VPN and a privacy browser to take the ad revenues and personal data revenues out of ‘em. ;)
Oh...sorry. Thought I’d already answered you question.
Quick search...
https://itsfoss.com/open-source-alternatives-android/
https://puri.sm/products/librem-5/
https://www.pine64.org/pinephone/
There were many more hits from
https://html.duckduckgo.com/html
with the keywords,
open source smart phone
I don’t know how many open source phones are out there, how many are stable or whether or not any of them are affordable.