That would be a question for the original maintainer, but I suspect it's a combination of issues like https://forums.gentoo.org/viewtopic-p-6191527.html and https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=833238 , so
CONFIG_FAT_DEFAULT_IOCHARSET="ascii"
FAT_DEFAULT_UTF8=y
is simply the most robust combination.
Pinned Comments
jonathon commented on 2022-01-11 19:25 (UTC) (edited on 2022-05-18 10:09 (UTC) by jonathon)
Please make sure you read the "How to use the AUR" wiki page before reporting issues: https://wiki.archlinux.org/index.php/Arch_User_Repository#Installing_and_upgrading_packages
A binary package is also available in my kernel-lts unofficial user repository.