I'm on Emacs29, compiled every 1 or two days, using

(set-face-attribute 'default nil :family "whatever" :height my-height)

to set my default font in ~/init.el and I've started needing

(define-key special-event-map [config-changed-event] 'ignore)

to avoid seeing it changed to the default mono font in my system... I've
learned the trick from

https://debbugs.gnu.org/cgi/bugreport.cgi?bug=25228#152

Proof-of-concept init.el file:
------------------------------------------------------------------------------------------------
;;
;; GUI
;;
(defun set-font (font-family font-size &optional line-space)
  "Set font, size and, optionally line-spacing"
  (message "using '%s' font" font-family)
  (setq-default line-spacing line-space) ; reset line-spacing when it is
not indicated
  (set-face-attribute 'default nil
                      :family font-family
                      :height font-size))

(set-font "Liberation Mono" 110 2)
;; (define-key special-event-map [config-changed-event] 'ignore)
(setq default-frame-alist '((width . 110) (height . 30)))
(message "That's it folks!")
------------------------------------------------------------------------------------------------
Like this it will reset the font to whatever the default monotype font is
defined in the system.
If you uncomment the (define-key line, you get the right font..

In GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.20, cairo version 1.16.0) of 2022-11-14 built on d0752a8af10b
Repository revision: 83a497ee879959cd1b052fa9138adb79b480394d
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12013000
System Description: Ubuntu 20.04.5 LTS

Configured using:
 'configure --prefix=/usr --program-suffix=29 --with-json --with-x
 --with-x-toolkit=gtk3 --with-cairo --with-compress-install
 --with-modules=yes --with-threads --with-included-regex --with-zlib
 --with-native-compilation 'CFLAGS=-g -O2
 -fdebug-prefix-map=/home/paag/emacs=. -fstack-protector-strong -Wformat
 -Werror=format-security' 'CPPFLAGS=-Wdate-time -D_FORTIFY_SOURCE=2'
 'LDFLAGS=-Wl,-Bsymbolic-functions -Wl,-z,relro''

Configured features:
CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG JSON
LIBSELINUX LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG
SECCOMP SOUND THREADS TIFF TOOLKIT_SCROLL_BARS X11 XDBE XIM XINPUT2 XPM
GTK3 ZLIB

Important settings:
  value of $LC_MONETARY: es_ES.UTF-8
  value of $LC_NUMERIC: es_ES.UTF-8
  value of $LC_TIME: es_ES.UTF-8
  value of $LANG: en_GB.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Fundamental

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  blink-cursor-mode: t
  buffer-read-only: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
/usr/share/emacs/site-lisp/latex-cjk-thai/thai-word hides
/usr/share/emacs/29.0.50/lisp/language/thai-word

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny dired
dired-loaddefs rfc822 mml mml-sec password-cache epa derived epg rfc6068
epg-config gnus-util text-property-search mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils time-date cl-loaddefs
comp comp-cstr warnings icons subr-x rx cl-seq cl-macs gv cl-extra
help-mode bytecomp byte-compile cl-lib rmc iso-transl tooltip cconv
eldoc paren electric uniquify ediff-hook vc-hooks lisp-float-type
elisp-mode mwheel term/x-win x-win term/common-win x-dnd tool-bar dnd
fontset image regexp-opt fringe tabulated-list replace newcomment
text-mode lisp-mode prog-mode register page tab-bar menu-bar rfn-eshadow
isearch easymenu timer select scroll-bar mouse jit-lock font-lock syntax
font-core term/tty-colors frame minibuffer nadvice seq simple cl-generic
indonesian philippine cham georgian utf-8-lang misc-lang vietnamese
tibetan thai tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek
romanian slovak czech european ethiopic indian cyrillic chinese
composite emoji-zwj charscript charprop case-table epa-hook
jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button loaddefs
theme-loaddefs faces cus-face macroexp files window text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget keymap
hashtable-print-readable backquote threads dbusbind inotify
dynamic-setting system-font-setting font-render-setting cairo
move-toolbar gtk x-toolkit xinput2 x multi-tty make-network-process
native-compile emacs)

Memory information:
((conses 16 78712 6045)
 (symbols 48 7113 0)
 (strings 32 19577 1968)
 (string-bytes 1 574200)
 (vectors 16 15742)
 (vector-slots 8 325249 11599)
 (floats 8 28 48)
 (intervals 56 234 0)
 (buffers 984 12))

-- 
Fragen sind nicht da um beantwortet zu werden,
Fragen sind da um gestellt zu werden
Georg Kreisler

Headaches with a Juju log:
unit-basic-16: 09:17:36 WARNING juju.worker.uniter.operation we should run
a leader-deposed hook here, but we can't yet