Unicode on Mac is insane. Mac OS X uses NFD while everything else uses NFC. This fixes that.

mac_utf8_insanity.md

convmv manpage

Install convmv if you don't have it

sudo apt-get install convmv

Convert all files in a directory from NFD to NFC:

convmv -r -f utf8 -t utf8 --nfc --notest .

Convert all files in a directory from NFC to NFD:

convmv -r -f utf8 -t utf8 --nfd --notest .

yup, that is exactly the madness with having two allowed but different character encodings for, say, the è (e-accent-grave)
the simple way to make sure both the media file and the vtt/srt file uses the same file name encoding is:

for i in *.mp4 ; do
mv -vn "$i" "$(syn2mac <<< "$i")"
done

and do the same for the subtitle files. You'll probably get a lot of "same file" warnings from mv on those files that were already in the target encoding.

Very nice tip!
On my Mac, I used brew install convmv, BTW.

You saved my day. Thank you!

Take a look at https://github.com/cr0sh/jaso for a faster alternative written in Rust.

$ brew install simnalamburt/x/jaso
$ jaso .
DONE; 100 files in 1.111529301 seconds

Just for reference, there is also NFCFN.py.