This is the only app of this kind that is simple enough for my grandma to use it and that works offline.

Birdnet iirc has separate recording, selecting, uploading, and results steps, which I tried to teach but it's too much. iNaturalist confuses even me about what buttons I'm supposed to be pressing if I just want to know what plant I'm looking at and not upload whatever (meta)data about me and my device to whatever (public?) database. Definitely recommend anyone to check out Whobird if you just want a simple, offline solution for bird sounds!

is there any FOSS app for plants?