Trying to set a default font

General system Applications
1

It is supposed to be a /etc/fonts/local.fonts files where system reads the default files so that I can make a file at ~/.config/fontconfig/fonts.conf and copy and modify its content for my user, but I can’t find that file. all I can see at /etc/fonts is this:

.
├── conf.d
│   ├── 10-hinting-slight.conf -> /usr/share/fontconfig/conf.default/10-hinting-slight.conf
│   ├── 10-scale-bitmap-fonts.conf -> /usr/share/fontconfig/conf.default/10-scale-bitmap-fonts.conf
│   ├── 10-sub-pixel-rgb.conf -> /usr/share/fontconfig/conf.default/10-sub-pixel-rgb.conf
│   ├── 10-yes-antialias.conf -> /usr/share/fontconfig/conf.default/10-yes-antialias.conf
│   ├── 11-lcdfilter-default.conf -> /usr/share/fontconfig/conf.default/11-lcdfilter-default.conf
│   ├── 20-unhint-small-dejavu-lgc-sans.conf -> /usr/share/fontconfig/conf.default/20-unhint-small-dejavu-lgc-sans.conf
│   ├── 20-unhint-small-dejavu-lgc-sans-mono.conf -> /usr/share/fontconfig/conf.default/20-unhint-small-dejavu-lgc-sans-mono.conf
│   ├── 20-unhint-small-dejavu-lgc-serif.conf -> /usr/share/fontconfig/conf.default/20-unhint-small-dejavu-lgc-serif.conf
│   ├── 20-unhint-small-dejavu-sans.conf -> /usr/share/fontconfig/conf.default/20-unhint-small-dejavu-sans.conf
│   ├── 20-unhint-small-dejavu-sans-mono.conf -> /usr/share/fontconfig/conf.default/20-unhint-small-dejavu-sans-mono.conf
│   ├── 20-unhint-small-dejavu-serif.conf -> /usr/share/fontconfig/conf.default/20-unhint-small-dejavu-serif.conf
│   ├── 20-unhint-small-vera.conf -> /usr/share/fontconfig/conf.default/20-unhint-small-vera.conf
│   ├── 30-metric-aliases.conf -> /usr/share/fontconfig/conf.default/30-metric-aliases.conf
│   ├── 40-nonlatin.conf -> /usr/share/fontconfig/conf.default/40-nonlatin.conf
│   ├── 44-source-han-sans-cn.conf -> /usr/share/fontconfig/conf.default/44-source-han-sans-cn.conf
│   ├── 44-source-han-sans-jp.conf -> /usr/share/fontconfig/conf.default/44-source-han-sans-jp.conf
│   ├── 44-source-han-sans-kr.conf -> /usr/share/fontconfig/conf.default/44-source-han-sans-kr.conf
│   ├── 45-generic.conf -> /usr/share/fontconfig/conf.default/45-generic.conf
│   ├── 45-latin.conf -> /usr/share/fontconfig/conf.default/45-latin.conf
│   ├── 46-noto-mono.conf -> /usr/share/fontconfig/conf.default/46-noto-mono.conf
│   ├── 46-noto-sans.conf -> /usr/share/fontconfig/conf.default/46-noto-sans.conf
│   ├── 46-noto-serif.conf -> /usr/share/fontconfig/conf.default/46-noto-serif.conf
│   ├── 48-spacing.conf -> /usr/share/fontconfig/conf.default/48-spacing.conf
│   ├── 49-sansserif.conf -> /usr/share/fontconfig/conf.default/49-sansserif.conf
│   ├── 50-user.conf -> /usr/share/fontconfig/conf.default/50-user.conf
│   ├── 51-local.conf -> /usr/share/fontconfig/conf.default/51-local.conf
│   ├── 57-dejavu-sans.conf -> /usr/share/fontconfig/conf.default/57-dejavu-sans.conf
│   ├── 57-dejavu-sans-mono.conf -> /usr/share/fontconfig/conf.default/57-dejavu-sans-mono.conf
│   ├── 57-dejavu-serif.conf -> /usr/share/fontconfig/conf.default/57-dejavu-serif.conf
│   ├── 58-dejavu-lgc-sans.conf -> /usr/share/fontconfig/conf.default/58-dejavu-lgc-sans.conf
│   ├── 58-dejavu-lgc-sans-mono.conf -> /usr/share/fontconfig/conf.default/58-dejavu-lgc-sans-mono.conf
│   ├── 58-dejavu-lgc-serif.conf -> /usr/share/fontconfig/conf.default/58-dejavu-lgc-serif.conf
│   ├── 60-generic.conf -> /usr/share/fontconfig/conf.default/60-generic.conf
│   ├── 60-latin.conf -> /usr/share/fontconfig/conf.default/60-latin.conf
│   ├── 65-fonts-persian.conf -> /usr/share/fontconfig/conf.default/65-fonts-persian.conf
│   ├── 65-nonlatin.conf -> /usr/share/fontconfig/conf.default/65-nonlatin.conf
│   ├── 66-noto-mono.conf -> /usr/share/fontconfig/conf.default/66-noto-mono.conf
│   ├── 66-noto-sans.conf -> /usr/share/fontconfig/conf.default/66-noto-sans.conf
│   ├── 66-noto-serif.conf -> /usr/share/fontconfig/conf.default/66-noto-serif.conf
│   ├── 69-unifont.conf -> /usr/share/fontconfig/conf.default/69-unifont.conf
│   ├── 69-urw-bookman.conf -> /usr/share/fontconfig/conf.default/69-urw-bookman.conf
│   ├── 69-urw-c059.conf -> /usr/share/fontconfig/conf.default/69-urw-c059.conf
│   ├── 69-urw-d050000l.conf -> /usr/share/fontconfig/conf.default/69-urw-d050000l.conf
│   ├── 69-urw-fallback-backwards.conf -> /usr/share/fontconfig/conf.default/69-urw-fallback-backwards.conf
│   ├── 69-urw-fallback-generics.conf -> /usr/share/fontconfig/conf.default/69-urw-fallback-generics.conf
│   ├── 69-urw-fallback-specifics.conf -> /usr/share/fontconfig/conf.default/69-urw-fallback-specifics.conf
│   ├── 69-urw-gothic.conf -> /usr/share/fontconfig/conf.default/69-urw-gothic.conf
│   ├── 69-urw-nimbus-mono-ps.conf -> /usr/share/fontconfig/conf.default/69-urw-nimbus-mono-ps.conf
│   ├── 69-urw-nimbus-roman.conf -> /usr/share/fontconfig/conf.default/69-urw-nimbus-roman.conf
│   ├── 69-urw-nimbus-sans.conf -> /usr/share/fontconfig/conf.default/69-urw-nimbus-sans.conf
│   ├── 69-urw-p052.conf -> /usr/share/fontconfig/conf.default/69-urw-p052.conf
│   ├── 69-urw-standard-symbols-ps.conf -> /usr/share/fontconfig/conf.default/69-urw-standard-symbols-ps.conf
│   ├── 69-urw-z003.conf -> /usr/share/fontconfig/conf.default/69-urw-z003.conf
│   ├── 80-delicious.conf -> /usr/share/fontconfig/conf.default/80-delicious.conf
│   ├── 90-synthetic.conf -> /usr/share/fontconfig/conf.default/90-synthetic.conf
│   └── README
└── fonts.conf

2 directories, 57 files
2

What DE are you using. For me ~/.config/fontconfig/fonts.conf got created by the lxqt settings.
In case you still need to configure it manually, here are example files:
https://wiki.archlinux.org/title/Font_configuration/Examples

I have the same folder /etc/fonts/conf.d and /etc/fonts/fonts.conf in place on my Arch install like you. Besides that there are no other files in /etc/fonts/

3

I am using Xfce. So it appears that it don’t depend on DE as it has nothing to do with it IMO.
There should be a xml file to setup default fonts there, like what is the default monospaced font is on the system, I can’t find it. I was trying to set up using this tutorial: How to Install and Manage Fonts on Linux - YouTube

4

Looks like Xfce has a GUI setting for this, not sure which config file it is writing/reading from:

5

Following this: https://wiki.archlinux.org/title/Font_configuration

I guess it looks recurseively in /usr/share/fonts/ and then creates ~/.config/fontconfig/fonts.conf