If you do crypto stuff on Android, use an open source keyboard that doesn't need connectivity permissions.

Floris board has decent feature parity to g keyboard except for autocorrect.
Options: Open board, Simple board.

Test them for yourself, but use f-droid to install them rather than apk files.

Chinese exists as a input language but there is no preset set up for it

Non latin inputs won't be integrated until v0.5.0 but there are a number of MacGyver like workarounds.

Non latin inputs won't be integrated until v0.5.0 but there are a number of MacGyver like workarounds.
https://github.com/florisboard/florisboard/issues/149

Securely typing Chinese characters is an issue best described by Naomi Wu

Securely typing Chinese characters is an issue best described by Naomi Wu https://twitter.com/RealSexyCyborg/status/1197695344575799296?t=C9q2rECKGHUbO-L6JdEkyQ&s=19

Languages are highly variable.

Floris has the most extensive language support but god help you  if your language is not a preset in the subtypes.