How to use locale(1) to set default paper size?

[Gleb Popov]

Hello hackers@

When I launch LibreOffice Writer, the default page size is set to "Letter".
>From what I read on Internets, the canonical way to set default paper size
is via locale(1). Many sites propose setting LC_PAPER env var to
ru_RU.UTF-8 to get "A4" as default size.

On FreeBSD, however, running `locale -ck` doesn't show a category for paper
size and setting LC_PAPER variable doesn't seem to work for LibreOffice.

Any ideas what can be done about that?