[Linux] MuseScore doesn't respect LC_PAPER variable and there is no way to set default page format

Issue type

UX/Interaction bug (incorrect behaviour)

Description with steps to reproduce

I use the en_US locale on my system as a default because I am comfortable with it, but since I live in Germany, I need to adjust certain locale settings to match my living circumstances. As an example, all paper here is A4. In accordance with how locale settings are managed on Linux, I set my LC_PAPER variable to de_DE.UTF-8 to ensure that programs use A4 as the default paper size. However, MuseScore doesn't seem to respect that and just sets all my scores to Letter anyway, with no option to change the default.

Steps to reproduce

1. be on Linux
2. edit /etc/locale.gen and uncomment en_US.UTF-8 and de_DE.UTF-8
3. run locale-gen as root
4. edit /etc/locale.conf as follows:

LANG=en_US.UTF-8
LC_PAPER=de_DE.UTF-8

5. reboot
6. open MuseScore and create a new score
7. Open Page settings

Expected behavior:

The page format is set to A4 by default

Actual behavior:

The page format is Letter / ANSI A

As a workaround, I would be happy if MuseScore exposed a global setting to change the default paper size for all new scores, but this is currently not an option.

Supporting files, videos and screenshots

https://github.com/user-attachments/assets/358e9df3-3a5d-4d26-87f3-9bc26181680c

In which versions of MuseScore Studio is this issue present?

4.5.2

Regression

I was unable to check

Operating system

Arch Linux

Additional context

No response

Checklist

• This report follows the guidelines for reporting bugs and issues
• I have verified that this issue has not been logged before, by searching the issue tracker for similar issues
• I have attached all requested files and information to this report
• I have attempted to identify the root problem as concisely as possible, and have used minimal reproducible examples where possible

Reproduce the issue on Linux using the reported LC_PAPER=de_DE.UTF-8 setup, then trace how new scores choose their initial page format and where Page settings gets its default. Done means new scores default to A4 when LC_PAPER specifies it, or a global default paper-size setting is available and works consistently.