I like this one, account is optional. No google at all.

https://f-droid.org/packages/com.team242.robozzle

or some classics

https://f-droid.org/packages/com.serwylo.retrowars

This one, I guess.

“The latest generation of ‘calculators’ (German synonym: computer), 16 colors, on a ‘solid plate’ (syn: hard drive) including mouse.”

“You should wait - it’s half the price in six months”

by Uli Stein

I always found the actual challenge to decide what to get rid of once the duplicates where found.

Some tools I tried would also ask file-by-file, which I found a bit useless for thousand of files. Yet, I cannot even express a set of rules to decide this in general, so I’m not blaming the tools.

In particular, with picture collections I also came to the conclusion that some redundancy is probably ok rather than accidentially deleting data that I duplicated on purpose and simply forgot why.