Traditionally, if you ran Emacs from a terminal, with no graphical display available, it used that terminal for its display.  With the pure GTK build of Emacs, this only works if you explicitly specify the –-no-window-system option.  Otherwise:

- - - - - - -
$ env DISPLAY= WAYLAND_DISPLAY= emacs -Q

(emacs:13745): Gtk-WARNING **: 11:12:58.299: cannot open display: 
$ echo $?
1
- - - - - - -


In GNU Emacs 29.3 (build 1, x86_64-redhat-linux-gnu, GTK+ Version
  3.24.41, cairo version 1.18.0) of 2024-04-26 built on
  cabaf4098b994f6da8ef60f3f6652faa
System Description: Fedora Linux 40 (Workstation Edition)

Configured using:
  'configure --build=x86_64-redhat-linux-gnu
  --host=x86_64-redhat-linux-gnu --program-prefix=
  --disable-dependency-tracking --prefix=/usr --exec-prefix=/usr
  --bindir=/usr/bin --sbindir=/usr/sbin --sysconfdir=/etc
  --datadir=/usr/share --includedir=/usr/include --libdir=/usr/lib64
  --libexecdir=/usr/libexec --localstatedir=/var --runstatedir=/run
  --sharedstatedir=/var/lib --mandir=/usr/share/man
  --infodir=/usr/share/info --with-cairo --with-dbus --with-gif
  --with-gpm=no --with-harfbuzz --with-jpeg --with-json --with-modules
  --with-native-compilation=aot --with-pgtk --with-png --with-rsvg
  --with-sqlite3 --with-tiff --with-tree-sitter --with-webp --with-xpm
  --with-xwidgets build_alias=x86_64-redhat-linux-gnu
  host_alias=x86_64-redhat-linux-gnu CC=gcc 'CFLAGS=-DMAIL_USE_LOCKF -O2
  -flto=auto -ffat-lto-objects -fexceptions -g -grecord-gcc-switches
  -pipe -Wall -Werror=format-security
  -Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=3 -Wp,-D_GLIBCXX_ASSERTIONS
  -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -fstack-protector-strong
  -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -march=x86-64
  -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection
  -fcf-protection -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer '
  LDFLAGS=-Wl,-z,relro
  PKG_CONFIG_PATH=:/usr/lib64/pkgconfig:/usr/share/pkgconfig CXX=g++
  'CXXFLAGS=-O2 -flto=auto -ffat-lto-objects -fexceptions -g
  -grecord-gcc-switches -pipe -Wall -Werror=format-security
  -Wp,-U_FORTIFY_SOURCE,-D_FORTIFY_SOURCE=3 -Wp,-D_GLIBCXX_ASSERTIONS
  -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -fstack-protector-strong
  -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -march=x86-64
  -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection
  -fcf-protection -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer ''

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG JSON
LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY
PDUMPER PGTK PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS TREE_SITTER WEBP XIM XWIDGETS GTK3 ZLIB

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

-- 
Peter Oliver