A paper-only journal would defend against the state, but not against people you live with. A digital journal can be encrypted, but an intelligence agency could potentially gain access (like, them reading your anti-government rants that may involve violence… that sort of stuff).
So… how to defend against both threats?
(Also, I just realized, paper journals cannot really be easily backed up…)
Typewriter with UV reactive ink would stop a cursory local glance, and could start a new hobby.
Edit: the old ribbon could be used as a backup.