Only Google Pixel devices are supported, new models are recommended. Source.
GrapheneOS
Only Google Pixel devices are supported, new models are recommended. Source .
Google PixelAndroidPhones
Listed in
GrapheneOS alternatives
LineageOS Wide range of supported devices: Open list .
Ubuntu Touch List of supported devices .
CalyxOS Only Google Pixel devices and Xiaomi Mi A2 are supported. Source .
AnySoftKeyboard Get it on F-Droid . Supports lots of languages via external packages.
OpenBoard Get it on F-Droid . No dependency on Google binaries.
FlorisBoard Get it on F-Droid . Currently in early-beta state.