https://bugs.winehq.org/show_bug.cgi?id=53598
--- Comment #6 from VZ vz-wine@zeitlins.org --- So after running wine under strace I found that it never looked for the fonts installed by the Debian fonts-wine package under /usr/share/wine/fonts at all. This seems to be due to the system configuration in /etc/fonts/fonts.conf, so it's probably not a Wine problem at all, but perhaps it should look in the Wine-specific directory in any case, at least as a fallback? If not, this bug should be just closed (and maybe another one should be opened for the Debian package...).
In any case, copying /usr/share/wine/fonts/marlett.ttf to ~/.local/share/fonts was enough to fix this issue -- just in case anybody else runs into it.