Running on systemd 252 (252.6-1) on Debian testing. It seems that systemd services, also transient ones, get the full set of locale environment variables (LANG, LANGUAGE, LC_*) as defined in /etc/default/locale.
I only have found environment variable $LANG mentioned in systemd.exec(5) as "Set or Propagated by the Service Manager". And I have found the following mentioned in locale.conf(5): Depending on the operating system, other configuration files might be checked for locale configuration as well, however only as fallback. I guess from that: 1) On Debian, systemd consults /etc/default/locale for locale settings as fallback. 2) systemd does not only propagate $LANG, but also all other locale-related environment variables to the processes it invokes. Is that correct? Is there any other systemd documentation on that which I might have missed? If not, should I open whatever doc bugs on GitHub to get the man page(s) extended? Thanks!
