My city has fully integrated the Transit app into our bus system, so you can also buy and scan your tickets within the app, including monthly passes and 10-use "punch cards". Just activate the QR code as you're boarding. It's awesome.

I personally use rdfind as it has an option to replace duplicates with hardlinks instead of deleting them outright (if on the same filesystem). This is useful if you do still need a file to exist at multiple paths.

I then use Czkawka for everything else, especially for similar, non-duplicate files.