This always gets brought up, and is the chicken-and-egg problem, but only sort of.

Supporting software designed for different platforms is not the phone’s responsibility. It should be the government and bank developers’ responsibility to build software for platforms their citizens and customers use.

Android and Apple do not jump through hoops to run Windows desktop software, for example, and the notion is kind of absurd to begin with. Yet this argument is used for Linux smartphones all the time.

Some of this also applies to people without phone / with dumbphone.

I know of:

• LineageOS
• LineageOS+microg (is its own thing)
• GrapheneOS - this is what I use
• eOS - shiny degoogled Android
• iodeOS - degoogled Android with some extra features and parental controls - might be something you want?

Some other Android-derived projects are inactive: DivestOS shut down, CalyxOS is paused.

For 3, I think it has to do with popularity, unlockability, and the chipset.

Edit: I stand corrected, see replies

(Not first-hand knowledge) I read somewhere that tonal languages such as Chinese make it difficult to express sarcasm the same way Indo-European languages do, with accent and inflection.