GNOME suddenly didn’t want to mount my USB pendrives. Dmesg said:
Unable to load NLS charset UTF8
FAT: IO charset UTF8 not found
The solution was to change NLS option in the kernel configuration. File systems -> DOS/FAT/NT Filesystems -> Default iocharset for FAT, set it to “utf8” (previously: “UTF-8”). This is a mess. UTF-8 should be always spelled as “UTF-8”, not “UTF8”, and I’m surprised that the case matters. Anyway, I’m crazy and I use Gentoo. If you want your linux to “just work”, install Ubuntu.