[BUG]: "warning: Setting locale failed"

[matmis]

What happened?

I configured the following in customisation:

• Capital city: Brussels (Belgium)
• Time zone: Europe/Brussels
• Keyboard layout: be

When I apt install something on the Pi, I get the following warning:

apt-listchanges: Can't set locale; make sure $LC_* and $LANG are correct!
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
        LANGUAGE = (unset),
        LC_ALL = (unset),
        LC_CTYPE = (unset),
        LC_NUMERIC = "nl_BE.UTF-8",
        LC_COLLATE = (unset),
        LC_TIME = "nl_BE.UTF-8",
        LC_MESSAGES = (unset),
        LC_MONETARY = "nl_BE.UTF-8",
        LC_ADDRESS = "nl_BE.UTF-8",
        LC_IDENTIFICATION = "en_US.UTF-8",
        LC_MEASUREMENT = "nl_BE.UTF-8",
        LC_PAPER = "nl_BE.UTF-8",
        LC_TELEPHONE = "en_DK.UTF-8",
        LC_NAME = "en_US.UTF-8",
        LANG = "en_GB.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to a fallback locale ("en_GB.UTF-8").
locale: Cannot set LC_ALL to default locale: No such file or directory

Version

2.0.7 (Default)

What host operating system were you using?

Debian and derivatives (eg Ubuntu)

Host OS Version

Kubuntu 24.04

Selected OS

Raspberry Pi OS Lite (64-bit) 2025-12-04

Which Raspberry Pi Device are you using?

Raspberry Pi 3B, 3A+, 3B+, and Compute Module 3, 3+

What kind of storage device are you using?

microSD Card in a USB reader

OS Customisation

• Yes, I was using OS Customisation when the bug occurred.

Relevant log output