I lived in Russia, and in History class I was taught that Stalin singlehandedly showed up to save those poor helpless Europeans from bloody nazis, because it was the right thing to do.
When I loved in Europe, it were the Jewish partisans who won WW2 through brain drain on Germany, and the stupid Nazis killed themselves.
In the US I found out that the thing in Europe was typical Medieval European Kingdoms in a fight, and the real high-tech stuff was in the Pacific.
Now as a programmer, I know who truly won WW2: it was our legendary bro Alan all along.
Some random notes app on F-droid probably has what you need. (Notes apps because “Diary” gives mostly medical/habit trackers/loggers)
Also check IzzyOnDroid repo (select “Writing” category or just search for “Diary”), it has more “modern” apps in my impression.
You will need to scroll through quite a few to find one you like. Just don’t get yourself into choice dilemma, pick one that looks decent and start using it.