Yes, Debian is being translated into Belarusian as well.
Mailing list: debian-l10n-belarusian
Status of PO files for language code: be — Belarusian
Status of Debconf templates l10n with PO files for language code: be — Belarusian
Other free software at translationproject.org
L10n/Belarusian (last modified 2018-08-22 14:46:44)