debian – How to configure the GNOME terminal in C.UTF-8?

I am having difficulty configuring the gnome terminal environment in C.UTF-8 locale, using Debian bullseye / GNOME3. I can update /etc/default/locale to LANG=C.UTF-8. After restart:

me@tesing:~$ localectl 
   System Locale: LANG=C.UTF-8
       VC Keymap: us
      X11 Layout: us

It looks good, but the following confuses me:

me@testing:~$ locale
LANG=en_US.UTF-8
LANGUAGE=
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC=en_US.UTF-8
LC_TIME=en_US.UTF-8
LC_COLLATE="en_US.UTF-8"
LC_MONETARY=en_US.UTF-8
LC_MESSAGES="en_US.UTF-8"
LC_PAPER=en_US.UTF-8
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT=en_US.UTF-8
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=

Two things caught my attention:

  1. localectl Y locale give different values ‚Äč‚Äčeven for LANG.
  2. According to locale, LANG/LC_NUMERIC/LC_TIME/LC_MONETARY/LC_PAPER/LC_MEASUREMENT are still stuck in en_US.UTF-8.

If i remove en_US.UTF-8 support by removing it from /etc/locale.genand rerun sudo locale-gen, the gnome terminal does not start, with an error in the registry – Regional settings not compatible with the C library. Using the regional backup settings & # 39; C & # 39 ;.

If I switch to the console using ctl + alt + F3, locale give as expected C.UTF-8.

What's going on?