about:support loads fine on linux - so this seems to be a Whonix issue
Firefox didn’t enable local translations until FF118 - Firefox 118.0, See All New Features, Updates and Fixes - and TB is based on ESR115 (and we didn’t enable it either)
Can you open issue at Issues · The Tor Project / Applications / Tor Browser · GitLab and provide more info, e.g. steps to reproduce: a site that triggers it, what your web-content language is, screenshot if you want, etc