I want (and plan) to have a flip phone one day, but work necessitates that I have a mobile OS that can support things like MFA, unfortunately.
I doubt you'd see many ads in the iPhone Assistive Access mode, which can (sort of) turn an iPhone into a feature phone. You might also need to swap out a few Apple apps though. https://support.apple.com/en-sg/guide/assistive-access-iphon...
I unfortunately didn't use it nearly as much as I thought I would have. It's also significantly bulkier in my pocket than my 13 mini. Loved the idea though.