neovide: Fontconfig error: Cannot load default config file

I wanted to tackle this issue https://github.com/neovim/neovim/issues/13416 but on my system (nixos) I get

Fontconfig warning: line 5: unknown element "description"
Fontconfig error: line 5: invalid attribute 'domain'
Fontconfig warning: "/etc/fonts/conf.d/10-hinting-slight.conf", line 4: unknown element "description"
Fontconfig warning: "/etc/fonts/conf.d/10-scale-bitmap-fonts.conf", line 4: unknown element "description"
Fontconfig warning: "/etc/fonts/conf.d/20-unhint-small-vera.conf", line 4: unknown element "description"
Fontconfig warning: "/etc/fonts/conf.d/30-metric-aliases.conf", line 4: unknown element "description"
Fontconfig warning: "/etc/fonts/conf.d/40-nonlatin.conf", line 4: unknown element "description"
Fontconfig warning: "/etc/fonts/conf.d/45-generic.conf", line 4: unknown element "description"
Fontconfig warning: "/etc/fonts/conf.d/45-latin.conf", line 4: unknown element "description"
Fontconfig warning: "/etc/fonts/conf.d/49-sansserif.conf", line 4: unknown element "description"
Fontconfig warning: "/etc/fonts/conf.d/50-user.conf", line 4: unknown element "description"
Fontconfig warning: "/etc/fonts/conf.d/51-local.conf", line 4: unknown element "description"
Fontconfig warning: "/etc/fonts/conf.d/60-generic.conf", line 4: unknown element "description"
Fontconfig warning: "/etc/fonts/conf.d/60-latin.conf", line 4: unknown element "description"
Fontconfig warning: "/etc/fonts/conf.d/65-nonlatin.conf", line 4: unknown element "description"
Fontconfig error: Cannot load default config file
thread 'main' panicked at 'fonts exist: NotFound', src/renderer/fonts/font_loader.rs:96:57
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

according to https://github.com/NixOS/nixpkgs/issues/94073#issuecomment-668722514 the problem doesn’t lie in the above errors but in incompatibilites between fontconfig versions: my nixos font cache uses a more recent version ( 2.13.92) than whatever neovide supports. I am not 100% sure but that’s my current guess at the problem. I dont know rust (willing to learn) but if you could share a patch or a workaround that would be very welcome.

NB: nix files I’ve been using https://github.com/teto/home/blob/master/nixpkgs/overlays/pkgs/neovide with https://github.com/teto/neovide/tree/nix