To be fair they’re ARM-based devices (most of them anyway) and linux works fine onthat architecture. The Raspberry Pi and others, Microsoft has Windows on ARM; as do the new M-series from Apple.
It’s all the obscure hardware, bootloading and vendor lock-in that kills it.
Can’t answer, really.
i’m ok with Tutanota for mail, although Proton does have an .onion address whereas Tutanota does not.
Bitwarden for passwords.
No VPN but i’d go for IVPN.